Trunk Ports

Trunk Ports #

What is a Trunk Port? #

Trunk ports are used to carry VLAN traffic between switches. They allow multiple VLANs to be transmitted over a single physical link, enabling efficient use of network resources and reducing the number of physical links required to connect switches.

When a port is configured as a trunk port, it is configured to carry traffic for multiple VLANs. This is different from an access port, which is configured to carry traffic for a single VLAN only. Trunk ports add a VLAN tag to each packet to identify which VLAN the packet belongs to. This tag is used to segregate traffic from different VLANs when it is transmitted over the trunk port.

Benefits of Using Trunk Ports #

Trunk ports provide several benefits when used in a network environment:

  1. Efficient use of network resources by reducing the number of physical links required to connect switches
  2. Simplifies network management and troubleshooting
  3. Improves network performance by reducing broadcast and multicast traffic
  4. Enhances network security by segregating traffic from different VLANs
  5. Scalability by allowing easy addition or removal of VLANs without requiring additional physical links.

Configuration of Trunk Ports #

Here is an example of configuring a trunk port on a Cisco device:

Step 1: Access the switch

To access the switch, connect a console cable to the console port of the switch and use PuTTY.

Step 2: Enter privileged EXEC mode

Type enable and press Enter to enter privileged EXEC mode.

Step 3: Enter configuration mode

conf t

Step 4: Configure the port as a trunk port

To configure a port as a trunk port, use the following commands:

interface interface-id
switchport mode trunk

For example, to configure port Fa0/24 as a trunk port, use the following commands:

Switch(config)# interface FastEthernet0/24
Switch(config-if)# switchport mode trunk

Step 5: Allow VLANs on the trunk

To allow specific VLANs on the trunk, use the following command:

switchport trunk allowed vlan vlan-list

For example, to allow VLANs 10, 20, and 30 on the trunk, use the following command:

Switch(config-if)# switchport trunk allowed vlan 10,20,30

Step 5: Verify Trunk Port Configuration

To verify trunk port configuration, use the following command:

show interfaces trunk

This command displays the trunk ports that have been configured on the switch, the VLANs that are allowed on each trunk port, and the status of each trunk port.