Multiple Spanning Tree Instance 0

[chris at marget.com (Chris Marget)]

On Wed, Feb 25, 2015 at 4:09 PM, Graham Johnston <johnstong at westmancom.com>
wrote:

> We are planning a migration from Rapid PVST+ to Multiple Spanning Tree to
> better support a mixed vendor environment.  My question today is about MST
> Instance 0.  In practice do you map any VLANs there other than VLAN 1?


I'd hoped to see some responses to this thread because I recently had some
awkward moments with a vendor after discovering that their switch wouldn't
allow me to map VLANs to STP instances in an arbitrary manner. I took the
position that the implementation was faulty, their position was more along
the lines of "Well, why would you want to do that anyway?"

Addressing the question directly, I know of two switching platforms which
force the operator to map VLANs other than 1 into instance 0.

Some Broadcom FASTPATH based platforms fail to mention VLAN 4094 in any
'show spanning-tree' commands, but always maps it to instance 0.

The implementation of MST available on Cumulus Linux only supports instance
0, maps all VLANs there. My Cumulus experience is a bit dated, this may
have changed in the last year.

/chris