1. Communication
1.1. Subnet Mask
1.2. IP address
1.2.1. Packet Matching Reply
1.2.2. echo reply
1.2.2.1. Indicates route valid
1.2.3. Forwarding Reply would match reverse
1.3. Default Gateway
1.4. Routing Table
1.4.1. Matching Routes
2. Normal Operations
2.1. Layer 3 Data
2.1.1. Data Path
2.1.1.1. Origin to Destination
2.2. Control Plane
2.2.1. Identify Protocol
2.2.1.1. Packet Forwarding
3. LAN Troubleshooting
3.1. CISCO Discovery Protocol
3.1.1. CDP
3.2. Interface Issues
3.2.1. Inverted Serial
3.2.2. No Clock Rate
3.2.3. Down Interface
3.2.4. No Cable Connection
3.2.5. Configuration
3.2.6. Loose Nut
3.3. Status Codes
3.3.1. Admin down
3.3.1.1. interface down
3.3.2. Down Down
3.3.2.1. Cabling Issue
3.3.2.2. Speed Mismatch
3.3.2.3. Duplex Mismatch
3.3.3. Up Down
3.3.3.1. LAN Interface
3.3.4. Down Down err
3.3.4.1. error disabled
3.3.4.1.1. port security
3.3.5. UP UP
3.3.5.1. Interface Working Properly
4. Commands
4.1. show cdp neighbors [number]
4.2. show cdp neighbors detail
4.3. show cdp entry [name]
5. VLAN Troubleshooting
5.1. Commands
5.1.1. Show Vlan /brief
5.1.2. show Vlan ID
5.1.3. show int type number switchport
5.1.4. show mac address-table dynamic