Multiple Spanning Tree Domains

[aloysius.liu]

Hi Gurus,

In my data center environment, we have deployed MST with a particular domain name A. However this site is already going to be vacate and we in progress of deployed another network environment in another DC using Nexus switch with MST as well. We need to connect these two site via layer 2 links in order to allow migration to take place in co-exist network. In the DC A, it is configure as MST instance 0 priority 0, & MST 1-2 with 8192 on the core 1 and core 2 switches. Is it safe or best practice to deploy MST in DC B with another domain name called B, the same MST instance 0 priority 0, & MST 1-2 with 8192 on the core 1 & 2 switches in DC B ? At the same time we have a cross-link between core switch 1 of DC A and core switch 1 of DC B to support the migration. Could allowing vlans and root guard configured on these interfaces of the cross link able to avoid potential loops?

[balaji.bandi]

you can not have same priority, if both same, then the spanning tree election process come in picture,. so better increast the priroty on the new site.

[aloysius.liu]

Hi,

Thanks for the reply, if on the new site, we did not hardcode on the priority and let the system specify itself, would this works as well though the MST domain name are different ? The cross-link are configured with root guard and allowing certain vlans. 

[MHM Cisco World]

"""NOTE NOTE check this solution before apply it"""
config 
BPDU filter in interface <- this will prevent one DC send BPDU to other DC 
BPDU guard in interface <- this will prevent by mistake enable STP in one side "one DC site".

deal with two DC as two separate STP domain, interconnect between them with ONE L2 connect. 

[Reza Sharifi]

Hi

Are you planning on putting the new site in the same region as the existing one? If you want to put them in the same region certain attributes must match. If they will be in different regions then it should not matter if the rest of the config is the same. Have a look at this document for more info:

https://networklessons.com/spanning-tree/multiple-spanning-tree-mst

HTH

[aloysius.liu]

Thanks for your reply,

They would be in a different region, DC A with MST region A while DC B with MST region B, however we need to have a L2 cross link across these sites to support migration. Thus in your reply, it doesn't have much effect, correct ?

[Reza Sharifi]

Correct. I think that should work just fine.

HTH