Why This Cheat Sheet Matters for CCNA
This cheat sheet covers the most important VLANs, Trunks, and Inter-VLAN Routing concepts tested on the CCNA (CCNA) certification exam. It contains 3 sections with 15 key points that you should memorize before exam day. Use this as a quick-reference guide during your final review sessions.
3Sections
15Key Points
VLAN Basics
- VLANs segment broadcast domains at Layer 2.
- VLAN 1 is the default VLAN — cannot be deleted. All ports are in VLAN 1 by default.
- VLANs 1002–1005 are reserved for Token Ring and FDDI.
- Extended VLAN range: 1006–4094 (requires VTP transparent mode or VTP v3).
- Each VLAN = one broadcast domain = one subnet.
Trunking
- 802.1Q is the standard trunking protocol. Inserts a 4-byte tag into the Ethernet frame.
- Native VLAN: untagged on the trunk. Default is VLAN 1. Should match on both ends.
- DTP (Dynamic Trunking Protocol): auto-negotiates trunk/access. Best practice: manually configure.
- switchport mode trunk — forces trunk mode.
- switchport mode access — forces access mode.
- switchport nonegotiate — disables DTP.
Inter-VLAN Routing
- Router-on-a-Stick: one router interface with sub-interfaces, each tagged with a VLAN.
- Layer 3 Switch with SVIs: interface vlan <id> with an IP address for each VLAN.
- ip routing must be enabled on the Layer 3 switch.
- Layer 3 switching is preferred in modern networks (faster, no external router needed).
Practice VLANs, Trunks, and Inter-VLAN Routing Questions
Put your knowledge to the test with practice questions.
Cisco Command Quick Reference
Cisco IOS commands follow a hierarchical structure: User EXEC mode (>), Privileged EXEC mode (#), Global Configuration mode (config)#, and Interface Configuration mode (config-if)#. Master the transitions between these modes and the key "show" commands for each technology area — they are heavily tested on every Cisco exam.