[c-nsp] MSTP between Cisco / Brocade

[Steven Raymond]

On Apr 25, 2012, at 5:08 PM, Randy wrote:

> Who is:
>  
> 0015.62b7.0dc0 with a bridge-priority of 16384?
>  
> That is the "who" the cisco is blocking.
>  
> From Brocade-output above:
>  
> Bridge: 80000024389c3d00 [Priority 32768, SysId 0, Mac 0024389c3d00]
> 
> ./Randy

The mac in question is the Cisco's:
ar01.prov#sh spanning-tree active 

MST0
  Spanning tree enabled protocol mstp
  Root ID    Priority    16384
             Address     0015.62b7.0dc0
             This bridge is the root


But nevermind I suppose, the issue is resolved with help from Brocade TAC.  The MLX defaults to "route-only" which apparently means every port acts like Cisco's equivalent to "no switchport" or layer-3 only mode.  So it would receive the MLX's BPDUs and silently discard them.  Here's the strange part, despite being set for "route-only", the MLX still transmits BPDUs.  Which the Cisco received, detected that the MLX said port role is "designated", and put it into blocking dispute since Cisco is the real root.

Is it common & expected for swouters to tx BPDUs when the port is in layer-3-only mode?  Or am I just not getting the idea behind "route-only" in Brocade?


Thanks for the help!