[c-nsp] Port-channel between Cisco 4948 and ASR 9k going err-disable

[Tom Hill]

On 11/10/16 12:00, David Wilkinson wrote:
> 4948 log:
> %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 1234: New Root Port is
> Port-channel2. New Root Mac Address is xxxx.xxxx.0cc0
> %SPANTREE-5-ROOTCHANGE: Root Changed for vlan 1234: New Root Port is
> Port-channel2. New Root Mac Address is xxxx.xxxx.0cc0
> %SPANTREE-5-TOPOTRAP: Topology Change Trap for vlan 1234
> %PM-4-ERR_DISABLE: channel-misconfig (STP) error detected on Po2,
> putting Te1/50 in err-disable state
> %EC-5-UNBUNDLE: Interface Te1/50 left the port-channel Po2
> %PM-4-ERR_DISABLE: channel-misconfig (STP) error detected on Po2,
> putting Te1/52 in err-disable state
> %EC-5-UNBUNDLE: Interface Te1/52 left the port-channel Po2
> %PM-4-ERR_DISABLE: channel-misconfig (STP) error detected on Po2,
> putting Po2 in err-disable state

I'm assuming you know what that device is that's claiming the root
bridge? That's probably a good clue.

Assuming PVST BPDUs are leaking across the VPLS instance, perhaps this
is (as Dragan alludes to) triggering the EtherChannel/STP
misconfiguration detection.

There's a good description here:

 http://www.cisco.com/c/en/us/support/docs/lan-switching/etherchannel/20625-127.html

With the split horizon forwarding inherent to VPLS, do you need PVST (or
STP in general) to run across these links?

Glad you posted though; I suspect I'll have to do something very similar
soon. :)

-- 
Tom