Friday, October 30, 2015

Setting up a Cisco port-channel

Setting up port-channels on a Cisco switch can sometimes be a real PITA due to your interface settings having to match the port-channel settings.  I’ve come up with a way to eliminate the config mismatches, which I’ll describe below.

First we clear the configuration on the interfaces that we’re going to add to our port-channel by doing a “default int gi1/1/1

Then we add our interfaces to the port-channel and only then do we configure our port-channel, like so:

int gi1/1/1
channel-group <x> mode active
int gi2/1/1
channel-group <x> mode active
int po<x>
switchport mode trunk
switchport trunk allowed vlan 10,50,...
switchport trunk native vlan 999

This forces your interfaces to join the port-channel before any configuration is added to them. It also reduces the mistake of having mismatched configuration on both interfaces, which could cause independent members in your port-channel.