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New Member

MST with vPC's

Hi

Say, for example, I am deploying a large amount of VLANs with a vPC toology.  So I would have no spanning tree loops.  Logically my topology looks like a single Core switch to Access switch link.  However, ideally I would like to only allow specific VLANs on each vPC.

I understand the MST recommendation that for an MST region I should allow all VLANs in that region over all trunk links involved in the region to avoid accidental traffic black holes.

However I don't really want to allow VLANs on a link to an edge switch when there are no ports in that VLAN on the edge switch.  So since I have no STP loops could I safely allow VLANs 1 to 100 on vPC 100, VLANs 101 to 200 on vPC 200 and so on but still have all VLANs in one MST instance ?  MST would still calculate vPC 100 and 200 as forwarding so my traffic still gets to where it needs to.  Only if I introduce a loop is there a potential problem.

I don't want to rely on VTP pruning and I can't create many MST instances and easily allocate vlans to each one because any VLAN could be required on any vPC.

So can I create 1 MST instance, map all VLANs to it and still safely remove specific VLANs from vPC's on a vPC by vPC basis ?

My alternative is to have my 1000 VLANs each running a rapid instance on each port they are active on when I really don't need all that overhead with no loops in the network. 

Thanks, Stuart.

  • Application Networking
1 REPLY
New Member

MST with vPC's

Stuart,

I think you posted your question in the wrong community. I think you will get a much faster answer if you post it here:

https://supportforums.cisco.com/community/netpro/network-infrastructure/switching

Cheers!

Stefan

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