DCs over vPC in order to Build DCI | What Happened when the DCI Link (vPC) goes down from STP point of view or others attributes

[Ibrahim Jamil]

Hi Guys

Consider we connect 2 DCs  over vPC in order to Build DCI

What Happened when the DCI Link (vPC) goes down from STP point of view or others attributes when such situation happened

thanks

[Sergiu.Daniluk]

Hello Ibrahim,

If DCI link goes down, following should be expected:

• in the DC where the STP root is configured, nothing will change from perspective of spanning tree
• in the second DC, a new STP root will be elected
• supposing you have HSRP configured on both vpc domains, with HSRP isolation, the servers should still reach it's gateway
• depending on how you have configured the connectivity with external network, and how prefixes are advertised, you may or may not have North-South connectivity.

Stay safe,

Sergiu

[Ibrahim Jamil]

Hi Sergiu

I ve configured both DCs to be independent from STP Domain point of view ,DC-1 has root primary/secondary and DC-2 has primary/secondary

on the port-channel i have filter BPDU using the command BPDU Filer

pls advise

Thanks

[balaji.bandi]

Its all depends on deployment, vPC has good features and command peer-switch.

Default nature of vPC only the primary switch will send BPDU’s to vPC member ports and  secondary won’t process any BPDU’s. Secondary receives a BPDU, it passed across the peer-link for the primary switch to process.

suggest approach peer-switch configured part of vPC, the command enables both the peer switches to send and process BPDU’s. Both switches will continue to use the same bridge ID, based on the System MAC.

One advantage to this is that there is less traffic loss during a peer-link restoration. Also, if there is a dual-active scenario, both switches process BPDU’s. This aids in switching loop prevention. Finally, if there is a primary/secondary switchover, this will reduce BPDU loss.

But when the split happens, they will be isolated they do not know each other, so they active their own way until they link restoration takes place.

That is the reason always suggest to have high available with dual-path different MPLS providers suggested. (this is the risk and limitation)

[Sergiu.Daniluk]

I think Ibrahim is referring to a topology where there are two vpc domains, one in each DC, with a back-to-back vpc between them.

So peer-switch doesn't help in this situation.

Cheers,

Sergiu

[Ibrahim Jamil]

Hi Balaji

Kindly,Elaborate more with regard to ur replay

thanks