Terminology Quick Sheet - Page 2

Computer Network

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

An office network connects laptops, printers, servers, Wi-Fi, firewall, and internet.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Computer Network in your own words.
• Draw where Computer Network appears in a small office network and a cloud network.
• Create one business use case for Computer Network.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Node

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A laptop, router, printer, server, IP phone, and camera are network nodes.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Node in your own words.
• Draw where Node appears in a small office network and a cloud network.
• Create one business use case for Node.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Host

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A Windows laptop with IP 192.168.1.25 is a host.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Host in your own words.
• Draw where Host appears in a small office network and a cloud network.
• Create one business use case for Host.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Client

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A browser is a web client when it opens an HR portal.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Client in your own words.
• Draw where Client appears in a small office network and a cloud network.
• Create one business use case for Client.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Server

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A payroll server provides payroll pages to employee browsers.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Server in your own words.
• Draw where Server appears in a small office network and a cloud network.
• Create one business use case for Server.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Peer-to-Peer Network

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Two laptops sharing files directly on the same LAN.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Peer-to-Peer Network in your own words.
• Draw where Peer-to-Peer Network appears in a small office network and a cloud network.
• Create one business use case for Peer-to-Peer Network.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Topology

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A star topology connects all office PCs to an access switch.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Topology in your own words.
• Draw where Topology appears in a small office network and a cloud network.
• Create one business use case for Topology.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Star Topology

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Employee desks connect to one access switch.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Star Topology in your own words.
• Draw where Star Topology appears in a small office network and a cloud network.
• Create one business use case for Star Topology.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Mesh Topology

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Data center switches have redundant paths.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Mesh Topology in your own words.
• Draw where Mesh Topology appears in a small office network and a cloud network.
• Create one business use case for Mesh Topology.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Bandwidth

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A 1 Gbps link can carry more traffic than a 100 Mbps link.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Bandwidth in your own words.
• Draw where Bandwidth appears in a small office network and a cloud network.
• Create one business use case for Bandwidth.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Throughput

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A 1 Gbps link may deliver 600 Mbps real file transfer throughput.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Throughput in your own words.
• Draw where Throughput appears in a small office network and a cloud network.
• Create one business use case for Throughput.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Latency

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A video meeting feels delayed if latency is very high.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Latency in your own words.
• Draw where Latency appears in a small office network and a cloud network.
• Create one business use case for Latency.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Jitter

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Voice calls become choppy when jitter is high.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Jitter in your own words.
• Draw where Jitter appears in a small office network and a cloud network.
• Create one business use case for Jitter.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Packet Loss

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

5% packet loss can make video meetings unstable.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Packet Loss in your own words.
• Draw where Packet Loss appears in a small office network and a cloud network.
• Create one business use case for Packet Loss.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Protocol

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

HTTP, DNS, TCP, and DHCP are protocols.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Protocol in your own words.
• Draw where Protocol appears in a small office network and a cloud network.
• Create one business use case for Protocol.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Packet

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A website response is split into many IP packets.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Packet in your own words.
• Draw where Packet appears in a small office network and a cloud network.
• Create one business use case for Packet.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Frame

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A switch forwards Ethernet frames inside a LAN.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Frame in your own words.
• Draw where Frame appears in a small office network and a cloud network.
• Create one business use case for Frame.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Segment

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A web download is carried in TCP segments.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Segment in your own words.
• Draw where Segment appears in a small office network and a cloud network.
• Create one business use case for Segment.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Bit

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Network speed is measured in bits per second.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Bit in your own words.
• Draw where Bit appears in a small office network and a cloud network.
• Create one business use case for Bit.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Encapsulation

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

HTTP data gets TCP, IP, and Ethernet headers.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Encapsulation in your own words.
• Draw where Encapsulation appears in a small office network and a cloud network.
• Create one business use case for Encapsulation.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Decapsulation

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A server extracts Ethernet, IP, TCP, then HTTP data.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Decapsulation in your own words.
• Draw where Decapsulation appears in a small office network and a cloud network.
• Create one business use case for Decapsulation.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

LAN

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Office users connect to printers and internal apps through the LAN.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of LAN in your own words.
• Draw where LAN appears in a small office network and a cloud network.
• Create one business use case for LAN.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

WAN

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Headquarters and branch offices are connected through a WAN.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of WAN in your own words.
• Draw where WAN appears in a small office network and a cloud network.
• Create one business use case for WAN.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

WLAN

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Corporate Wi-Fi and guest Wi-Fi are WLANs.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of WLAN in your own words.
• Draw where WLAN appears in a small office network and a cloud network.
• Create one business use case for WLAN.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

MAN

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A university connects city campus buildings using MAN links.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of MAN in your own words.
• Draw where MAN appears in a small office network and a cloud network.
• Create one business use case for MAN.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

PAN

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A phone connected to wireless earbuds over Bluetooth.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of PAN in your own words.
• Draw where PAN appears in a small office network and a cloud network.
• Create one business use case for PAN.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

VPN

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Remote employees use VPN with MFA to access internal apps.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of VPN in your own words.
• Draw where VPN appears in a small office network and a cloud network.
• Create one business use case for VPN.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

OSI Model

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Cable is Layer 1, VLAN/MAC is Layer 2, IP routing is Layer 3.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of OSI Model in your own words.
• Draw where OSI Model appears in a small office network and a cloud network.
• Create one business use case for OSI Model.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

TCP/IP Model

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Ethernet is Link, IP is Internet, TCP/UDP is Transport.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of TCP/IP Model in your own words.
• Draw where TCP/IP Model appears in a small office network and a cloud network.
• Create one business use case for TCP/IP Model.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Physical Layer

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A bad cable causes a Layer 1 issue.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Physical Layer in your own words.
• Draw where Physical Layer appears in a small office network and a cloud network.
• Create one business use case for Physical Layer.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Data Link Layer

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A switch forwards frames using MAC addresses.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Data Link Layer in your own words.
• Draw where Data Link Layer appears in a small office network and a cloud network.
• Create one business use case for Data Link Layer.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Network Layer

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A router forwards traffic between subnets.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Network Layer in your own words.
• Draw where Network Layer appears in a small office network and a cloud network.
• Create one business use case for Network Layer.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Transport Layer

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

HTTPS uses TCP port 443.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Transport Layer in your own words.
• Draw where Transport Layer appears in a small office network and a cloud network.
• Create one business use case for Transport Layer.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Application Layer

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A DNS issue is an application-layer service issue.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Application Layer in your own words.
• Draw where Application Layer appears in a small office network and a cloud network.
• Create one business use case for Application Layer.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

NIC

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A laptop Wi-Fi adapter and Ethernet port are NICs.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of NIC in your own words.
• Draw where NIC appears in a small office network and a cloud network.
• Create one business use case for NIC.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Switch

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

An access switch connects employee laptops to the office LAN.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Switch in your own words.
• Draw where Switch appears in a small office network and a cloud network.
• Create one business use case for Switch.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Router

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A router connects a branch LAN to headquarters.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Router in your own words.
• Draw where Router appears in a small office network and a cloud network.
• Create one business use case for Router.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Firewall

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A firewall allows HTTPS and blocks unauthorized SSH.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Firewall in your own words.
• Draw where Firewall appears in a small office network and a cloud network.
• Create one business use case for Firewall.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Access Point

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Ceiling APs provide corporate and guest Wi-Fi.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Access Point in your own words.
• Draw where Access Point appears in a small office network and a cloud network.
• Create one business use case for Access Point.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Modem

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A cable modem connects a firewall/router to the ISP.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Modem in your own words.
• Draw where Modem appears in a small office network and a cloud network.
• Create one business use case for Modem.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Gateway

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A default gateway lets hosts leave their subnet.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Gateway in your own words.
• Draw where Gateway appears in a small office network and a cloud network.
• Create one business use case for Gateway.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Load Balancer

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A load balancer sends web traffic to three app servers.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Load Balancer in your own words.
• Draw where Load Balancer appears in a small office network and a cloud network.
• Create one business use case for Load Balancer.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Proxy Server

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A corporate web proxy filters and logs internet browsing.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Proxy Server in your own words.
• Draw where Proxy Server appears in a small office network and a cloud network.
• Create one business use case for Proxy Server.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Hub

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Old labs used hubs before switches became common.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Hub in your own words.
• Draw where Hub appears in a small office network and a cloud network.
• Create one business use case for Hub.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

IDS

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

IDS alerts when a host scans many ports.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of IDS in your own words.
• Draw where IDS appears in a small office network and a cloud network.
• Create one business use case for IDS.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

IPS

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

IPS blocks exploit traffic at the internet edge.

5. Step-by-Step Troubleshooting Flow

1. Identify source and destination.
2. Check local settings.
3. Check path and security controls.
4. Check service health.
5. Document root cause.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Memorizing without a diagram.
• Skipping basic checks.
• No documentation.
• Ignoring security and business impact.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of IPS in your own words.
• Draw where IPS appears in a small office network and a cloud network.
• Create one business use case for IPS.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

MAC Address

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

00:1A:2B:3C:4D:5E is a MAC address.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of MAC Address in your own words.
• Draw where MAC Address appears in a small office network and a cloud network.
• Create one business use case for MAC Address.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

IP Address

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A laptop may have IP address 10.10.5.25.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of IP Address in your own words.
• Draw where IP Address appears in a small office network and a cloud network.
• Create one business use case for IP Address.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

IPv4

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

192.168.1.10 is an IPv4 address.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of IPv4 in your own words.
• Draw where IPv4 appears in a small office network and a cloud network.
• Create one business use case for IPv4.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

IPv6

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

2001:db8:abcd::10 is an IPv6 address.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of IPv6 in your own words.
• Draw where IPv6 appears in a small office network and a cloud network.
• Create one business use case for IPv6.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Public IP Address

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A website load balancer may use a public IP.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Public IP Address in your own words.
• Draw where Public IP Address appears in a small office network and a cloud network.
• Create one business use case for Public IP Address.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Private IP Address

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

10.0.0.0/8 and 192.168.0.0/16 are private ranges.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Private IP Address in your own words.
• Draw where Private IP Address appears in a small office network and a cloud network.
• Create one business use case for Private IP Address.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Subnet

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

10.10.10.0/24 can be an employee subnet.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Subnet in your own words.
• Draw where Subnet appears in a small office network and a cloud network.
• Create one business use case for Subnet.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Subnet Mask

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

255.255.255.0 is the mask for /24.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Subnet Mask in your own words.
• Draw where Subnet Mask appears in a small office network and a cloud network.
• Create one business use case for Subnet Mask.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

CIDR

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

10.0.0.0/16 is a CIDR block.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of CIDR in your own words.
• Draw where CIDR appears in a small office network and a cloud network.
• Create one business use case for CIDR.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Network ID

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

192.168.1.0 is the network ID of 192.168.1.0/24.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Network ID in your own words.
• Draw where Network ID appears in a small office network and a cloud network.
• Create one business use case for Network ID.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Broadcast Address

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

192.168.1.255 is the broadcast of 192.168.1.0/24.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Broadcast Address in your own words.
• Draw where Broadcast Address appears in a small office network and a cloud network.
• Create one business use case for Broadcast Address.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Usable Host Range

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

192.168.1.1 to 192.168.1.254 in a /24.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Usable Host Range in your own words.
• Draw where Usable Host Range appears in a small office network and a cloud network.
• Create one business use case for Usable Host Range.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Default Gateway

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A laptop uses 10.10.5.1 as gateway.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Default Gateway in your own words.
• Draw where Default Gateway appears in a small office network and a cloud network.
• Create one business use case for Default Gateway.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

ARP

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A laptop asks who has 10.10.5.1 to find the gateway MAC.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of ARP in your own words.
• Draw where ARP appears in a small office network and a cloud network.
• Create one business use case for ARP.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Neighbor Discovery

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

IPv6 hosts use Neighbor Discovery instead of ARP.

5. Step-by-Step Troubleshooting Flow

1. Check IP address, subnet mask/prefix, gateway, and DNS.
2. Confirm the IP belongs to the correct subnet and VLAN.
3. Ping the default gateway.
4. Check for duplicate IP address.
5. Verify route and firewall after gateway.

6. Useful Commands / Verification Checks

Windows: ipconfig /all
Linux/macOS: ip addr && ip route
Test: ping <default-gateway>
Verify: IP, mask/prefix, gateway, DNS, duplicate IP

7. Common Mistakes

• Wrong subnet mask or prefix.
• Default gateway outside the subnet.
• Duplicate IP address.
• No documented IP plan.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Neighbor Discovery in your own words.
• Draw where Neighbor Discovery appears in a small office network and a cloud network.
• Create one business use case for Neighbor Discovery.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Ethernet

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Office PCs connect to switches using Ethernet cables.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Ethernet in your own words.
• Draw where Ethernet appears in a small office network and a cloud network.
• Create one business use case for Ethernet.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

VLAN

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

VLAN 10 for employees, VLAN 20 for servers, VLAN 30 for guests.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of VLAN in your own words.
• Draw where VLAN appears in a small office network and a cloud network.
• Create one business use case for VLAN.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Access Port

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A laptop port assigned to VLAN 10.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Access Port in your own words.
• Draw where Access Port appears in a small office network and a cloud network.
• Create one business use case for Access Port.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Trunk Port

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Switch uplink carries VLANs 10, 20, and 30.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Trunk Port in your own words.
• Draw where Trunk Port appears in a small office network and a cloud network.
• Create one business use case for Trunk Port.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Native VLAN

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Both trunk ends should agree on the native VLAN.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Native VLAN in your own words.
• Draw where Native VLAN appears in a small office network and a cloud network.
• Create one business use case for Native VLAN.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

MAC Address Table

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Switch learns a laptop MAC on port Gi1/0/5.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of MAC Address Table in your own words.
• Draw where MAC Address Table appears in a small office network and a cloud network.
• Create one business use case for MAC Address Table.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Broadcast Domain

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

One VLAN is typically one broadcast domain.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Broadcast Domain in your own words.
• Draw where Broadcast Domain appears in a small office network and a cloud network.
• Create one business use case for Broadcast Domain.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Collision Domain

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Old hubs created large collision domains.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Collision Domain in your own words.
• Draw where Collision Domain appears in a small office network and a cloud network.
• Create one business use case for Collision Domain.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

STP

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

STP blocks one redundant path between switches.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of STP in your own words.
• Draw where STP appears in a small office network and a cloud network.
• Create one business use case for STP.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

LACP

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Two switch uplinks are bundled for more capacity and redundancy.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of LACP in your own words.
• Draw where LACP appears in a small office network and a cloud network.
• Create one business use case for LACP.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

PoE

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

IP phones and access points receive power from PoE switch ports.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of PoE in your own words.
• Draw where PoE appears in a small office network and a cloud network.
• Create one business use case for PoE.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Speed and Duplex

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A duplex mismatch can cause poor performance.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Speed and Duplex in your own words.
• Draw where Speed and Duplex appears in a small office network and a cloud network.
• Create one business use case for Speed and Duplex.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Copper Cable

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Cat6 cable connects desk ports to a switch.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Copper Cable in your own words.
• Draw where Copper Cable appears in a small office network and a cloud network.
• Create one business use case for Copper Cable.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Fiber Cable

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Fiber connects buildings or data center switches.

5. Step-by-Step Troubleshooting Flow

1. Check physical link and cable.
2. Check switch port status and errors.
3. Confirm access VLAN or trunk allowed VLAN.
4. Check MAC address table.
5. Check STP state and gateway reachability.

6. Useful Commands / Verification Checks

show interfaces status
show vlan brief
show interfaces trunk
show mac address-table
show spanning-tree
Verify: port, VLAN, trunk, MAC learning, STP

7. Common Mistakes

• Wrong VLAN on access port.
• Trunk missing required VLAN.
• Layer 2 loop without STP protection.
• Ignoring interface errors.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Fiber Cable in your own words.
• Draw where Fiber Cable appears in a small office network and a cloud network.
• Create one business use case for Fiber Cable.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

DNS

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

payroll.company.com resolves to 10.20.5.30.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

nslookup <name>
dig <name> A
dig <domain> MX
dig @8.8.8.8 <name>
Verify: record, resolver, TTL, authoritative answer

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of DNS in your own words.
• Draw where DNS appears in a small office network and a cloud network.
• Create one business use case for DNS.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

DNS Resolver

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A laptop uses corporate DNS resolver 10.1.1.10.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

nslookup <name>
dig <name> A
dig <domain> MX
dig @8.8.8.8 <name>
Verify: record, resolver, TTL, authoritative answer

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of DNS Resolver in your own words.
• Draw where DNS Resolver appears in a small office network and a cloud network.
• Create one business use case for DNS Resolver.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Authoritative DNS Server

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Authoritative DNS for company.com stores its public records.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

nslookup <name>
dig <name> A
dig <domain> MX
dig @8.8.8.8 <name>
Verify: record, resolver, TTL, authoritative answer

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Authoritative DNS Server in your own words.
• Draw where Authoritative DNS Server appears in a small office network and a cloud network.
• Create one business use case for Authoritative DNS Server.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

A Record

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

app.company.com A 203.0.113.10.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

nslookup <name>
dig <name> A
dig <domain> MX
dig @8.8.8.8 <name>
Verify: record, resolver, TTL, authoritative answer

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of A Record in your own words.
• Draw where A Record appears in a small office network and a cloud network.
• Create one business use case for A Record.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

AAAA Record

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

app.company.com AAAA 2001:db8::10.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

nslookup <name>
dig <name> A
dig <domain> MX
dig @8.8.8.8 <name>
Verify: record, resolver, TTL, authoritative answer

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of AAAA Record in your own words.
• Draw where AAAA Record appears in a small office network and a cloud network.
• Create one business use case for AAAA Record.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

CNAME Record

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

www.company.com CNAME company-web.cloudhost.com.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

nslookup <name>
dig <name> A
dig <domain> MX
dig @8.8.8.8 <name>
Verify: record, resolver, TTL, authoritative answer

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of CNAME Record in your own words.
• Draw where CNAME Record appears in a small office network and a cloud network.
• Create one business use case for CNAME Record.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

MX Record

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

company.com MX 10 mail.company.com.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

nslookup <name>
dig <name> A
dig <domain> MX
dig @8.8.8.8 <name>
Verify: record, resolver, TTL, authoritative answer

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of MX Record in your own words.
• Draw where MX Record appears in a small office network and a cloud network.
• Create one business use case for MX Record.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

TXT Record

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

SPF, DKIM, and DMARC use TXT records.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

nslookup <name>
dig <name> A
dig <domain> MX
dig @8.8.8.8 <name>
Verify: record, resolver, TTL, authoritative answer

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of TXT Record in your own words.
• Draw where TXT Record appears in a small office network and a cloud network.
• Create one business use case for TXT Record.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

PTR Record

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Mail systems may check PTR records.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

nslookup <name>
dig <name> A
dig <domain> MX
dig @8.8.8.8 <name>
Verify: record, resolver, TTL, authoritative answer

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of PTR Record in your own words.
• Draw where PTR Record appears in a small office network and a cloud network.
• Create one business use case for PTR Record.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

TTL

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A TTL of 300 seconds means cache for 5 minutes.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

nslookup <name>
dig <name> A
dig <domain> MX
dig @8.8.8.8 <name>
Verify: record, resolver, TTL, authoritative answer

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of TTL in your own words.
• Draw where TTL appears in a small office network and a cloud network.
• Create one business use case for TTL.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

DHCP

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Laptop gets IP, gateway, and DNS after joining Wi-Fi.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

Windows: ipconfig /all && ipconfig /renew
Linux: sudo dhclient -v
Verify: lease IP, scope, gateway option, DNS option

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of DHCP in your own words.
• Draw where DHCP appears in a small office network and a cloud network.
• Create one business use case for DHCP.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

DHCP Scope

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

VLAN 10 DHCP scope gives 10.10.10.50-10.10.10.200.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

Windows: ipconfig /all && ipconfig /renew
Linux: sudo dhclient -v
Verify: lease IP, scope, gateway option, DNS option

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of DHCP Scope in your own words.
• Draw where DHCP Scope appears in a small office network and a cloud network.
• Create one business use case for DHCP Scope.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

DHCP Lease

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Laptop leases 10.10.10.70 for 24 hours.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

Windows: ipconfig /all && ipconfig /renew
Linux: sudo dhclient -v
Verify: lease IP, scope, gateway option, DNS option

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of DHCP Lease in your own words.
• Draw where DHCP Lease appears in a small office network and a cloud network.
• Create one business use case for DHCP Lease.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

DORA Process

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

A new laptop discovers DHCP and accepts an offered IP.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

Windows: ipconfig /all && ipconfig /renew
Linux: sudo dhclient -v
Verify: lease IP, scope, gateway option, DNS option

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of DORA Process in your own words.
• Draw where DORA Process appears in a small office network and a cloud network.
• Create one business use case for DORA Process.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

NAT

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Private office users access internet through one public IP.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of NAT in your own words.
• Draw where NAT appears in a small office network and a cloud network.
• Create one business use case for NAT.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

PAT

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

100 laptops browse internet through one firewall public IP.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of PAT in your own words.
• Draw where PAT appears in a small office network and a cloud network.
• Create one business use case for PAT.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

TCP

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

HTTPS and SSH use TCP.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of TCP in your own words.
• Draw where TCP appears in a small office network and a cloud network.
• Create one business use case for TCP.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

UDP

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

DNS, DHCP, voice, and video often use UDP.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of UDP in your own words.
• Draw where UDP appears in a small office network and a cloud network.
• Create one business use case for UDP.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Port

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

HTTPS uses TCP 443; DNS uses UDP/TCP 53.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Port in your own words.
• Draw where Port appears in a small office network and a cloud network.
• Create one business use case for Port.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

Socket

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

10.20.5.30:443/TCP is a web server socket.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of Socket in your own words.
• Draw where Socket appears in a small office network and a cloud network.
• Create one business use case for Socket.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

TCP Three-Way Handshake

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Browser opens TCP 443 before HTTPS data.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of TCP Three-Way Handshake in your own words.
• Draw where TCP Three-Way Handshake appears in a small office network and a cloud network.
• Create one business use case for TCP Three-Way Handshake.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

ICMP

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

ping uses ICMP echo request/reply.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task

• Write a 5-line explanation of ICMP in your own words.
• Draw where ICMP appears in a small office network and a cloud network.
• Create one business use case for ICMP.
• Run or document the related verification checks in a safe lab.
• Write one possible failure and how you would troubleshoot it.

10. Portfolio Evidence

HTTP

1. Definition

2. Detailed Explanation

3. Business Use Case

4. Real-World Example

Browser sends HTTP GET request.

5. Step-by-Step Troubleshooting Flow

1. Confirm the service name or IP.
2. Check DNS if a name is used.
3. Check port and protocol.
4. Test with curl, nslookup, dig, netstat, ss, or packet capture.
5. Review client, firewall, and server logs.

6. Useful Commands / Verification Checks

General checks:
1. Identify source and destination
2. Check link/IP/subnet/gateway/DNS
3. Check route/path
4. Check port/protocol/firewall
5. Check logs
6. Document result

7. Common Mistakes

• Testing only ping and ignoring service port.
• Wrong DNS or DHCP option.
• Firewall blocks required port.
• Logs not checked.

8. Interview Answer Format

9. Practice Task