Changing Trunk Ports on a Cisco 2970 Switch

Today I had to change trunk/uplink ports from port 1 to port 24 on a Cisco Catalyst 2970 switch. It is running IOS 12.2. Here are the steps that I took to get the job done via the CLI. It’s important to note that Spanning-tree Portfast can never be enabled on any port that is configured to be a Trunk/Uplink port.

1. Enter Configure mode. “config t”

2. Select the port you want to configure. “int g0/24”

3. Select the Switchport Trunk Encapsulation mode. “switchport trunk encapsulation dot1q”

4. Initialize the Trunk. “switchport mode trunk”

5. Turn off Spanning-tree Portfast on the new Trunk port. “no spanning-tree portfast”

6. Change to the old trunk port. “exit” “int g0/1”

7. Turn off the old trunk port. “no switchport mode trunk” “no switchport trunk encapsulation dot1q”

8. Turn on Spanning-tree Portfast on the old trunk port. “spanning-tree portfast”

9. Escape from the port and configuration modes and save your changes. “exit” “exit” “write mem”

That’s all there is to it! Now you can use port 24 to uplink the switch.

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