I setup the LAG on the 6224 stack with:
interface range ethernet 1/g24,2/g24
channel-group 24 mode auto
And on the Cisco 2960-S:
Interface range gi1/0/47,gi1/0/48
channel-group 1 mode active
The LAG would be active for a few moment then one of the 2960-S ports would turn orange, with interface status 'err-disabled'
I thought maybe spanning tree was blocking the ports, but this was not the case:
show spanning-tree blocked-ports
Further troubleshooting, I set both of the channel groups to static LAG thinking it might not be negotiating LACP correctly:
Dell 6224 stack:
interface range ethernet 1/g24,2/g24
channel-group 24 mode on
Cisco 2960-S:
Interface range gi1/0/47,gi1/0/48
channel-group 1 mode on
The LAG was still taking a dive :(
Troubleshooting, etherchannel debugging was enabled on the Cisco
Cisco 2960-S:
Interface range gi1/0/47,gi1/0/48
shutdown
no shutdown
With debugging enabled we could see that the 2960-S was erroring the ports because PAgP could not be negotiated!! We didn't ask for PAgP in the first place. PAgP is Cisco proprietary and not supported on other vendors switches.
The solution was to set the channel group on the Cisco to 'passive' mode :)
Dell 6224 stack:
channel-group 24 mode auto
Cisco 2960-S:
Interface range gi1/0/47,gi1/0/48
channel-group 1 mode passive
You can check to see if the LAG is passing VLAN trunk with this command on the Cisco 2960-S:
Inter-vendor switch connectivity issues eh!! This seems to only be the case with 2960's as the 3750's where fine. Thanks to Paul Walton for his troubleshooting.
