What is the best practice when configuring etherchannel on Cisco switches to prevent a STP loop/broadcast storm when etherchannel is mis-configured?
I had an instance where 2 ports on a switch were configured with via trunk ports properly however the opposing switch was only had one port switch as a trunk, the 2nd as a regular access port. Upon a power-cycle, a broadcast storm took down the network and originated from these two switches.
channel-group 1 mode on was configured on all ports.
From my research L2 etherchannel links should be configured with only
channel-group 1 mode desirable
L3 links can be configured w/ channel-group 1 mode on as STP isn't running over them.
Unfortunately in this scenario PVST+ was configured and bdpuguard was missing on all edge ports :( Lastly, all switches here are Cisco - not a multi-vendor environment