I had an outage between datacentres. I have a L2 gigabit link which is actually a member of an Etherchannel that is nailed up at both ends using "channel-group x mode on". There is only one member right now so a second link can be easily added in the future. Our provider did some "maintenance" and both ends of the channel err-disabled. When I tried to shut / no shut the link it kept immediately erroring out at both ends. I switched on some debugs at one site to investigate and received the below.
Code:
.Sep 22 23:51:19: FEC: pagp_switch_is_in_port_channel: Gi1/30 is not part of any agport
.Sep 22 23:51:19: FEC: pagp_switch_is_in_port_channel: Gi1/30 is not part of any agport
.Sep 22 23:51:21: FEC: pagp_switch_is_in_port_channel: Gi1/30 is not part of any agport
.Sep 22 23:51:21: FEC: pagp_switch_is_in_port_channel: Gi1/30 is not part of any agport
.Sep 22 23:51:22: FEC: pagp_switch_is_in_port_channel: Gi1/30 is not part of any agport
.Sep 22 23:51:22: FEC: pagp_switch_is_in_port_channel: Gi1/30 is not part of any agport
.Sep 22 23:51:22: FEC: pagp_switch_is_in_port_channel: Gi1/30 is not part of any agport
.Sep 22 23:51:51: FEC: pagp_switch_is_in_port_channel: Gi1/30 is not part of any agport
.Sep 22 23:51:53: FEC: pagp_switch_is_in_port_channel: Gi1/30 is not part of any agport
.Sep 22 23:51:53: FEC: pagp_switch_is_in_port_channel: Gi1/30 is not part of any agport
.Sep 22 23:51:56: %PM-4-ERR_DISABLE: channel-misconfig error detected on Gi1/30, putting Gi1/30 in err-disable state
We do not use PAgP anywhere on our network. I think our provider reconnected our link into another customer of theirs somewhere and I was receiving their other customers PAgP packets. After a short while and they put me on mute so they could confir with their engineer (whilst this was going on I rebuilt the channels from scratch) then I was able to bring up both sides without any errors. They did not say if they did make a patch mistake or not but I think it looks that way?