2.0 CCNA - Network Access

2.2 Configure and verify interswitch connectivity

Trunk ports, 802.1Q, and Native VLAN

Trunk ports, 802.1Q, and the Native VLAN are important concepts in CCNA that are related to the configuration of VLANs in a network.

• 1. Trunk ports: Trunk ports are switch ports that are used to carry traffic for multiple VLANs. A trunk port allows traffic from multiple VLANs to pass through a single physical link, providing inter-VLAN connectivity. Trunk ports are typically used to connect switches together and allow for the exchange of VLAN information between switches.

• 2. 802.1Q: 802.1Q is a networking standard that defines a method for inserting VLAN information into Ethernet frames. It is used to identify which VLAN a frame belongs to and is essential for inter-VLAN communication. 802.1Q uses a 4-byte tag in the Ethernet frame to carry the VLAN information, making it possible for switches to identify and forward traffic for specific VLANs.

• 3. Native VLAN: The Native VLAN is a VLAN that is associated with a trunk port and is used to carry untagged traffic. This means that traffic that is not assigned to a specific VLAN will be sent over the Native VLAN. By default, the Native VLAN is typically VLAN 1, but it can be changed to another VLAN if desired.

To configure trunk ports and 802.1Q, you need to:

• 1. Enable trunking on the port:

  • Enter interface configuration mode for the desired port using the "interface [port]" command.

  • Configure the port as a trunk using the "switchport mode trunk" command.