Loop L2-Migration Legacy FabricPath to ACI

[Danny Koenig]

Hi Community,

Need your help to solve this issue. I've read many manuals but no way out.

I want to migrate a legacy network running with Cisco Nexus switches and FEXes to ACI Multi-Pod, VLAN by VLAN. For visualization, please see plan below.

BD=EPG=VLAN connected to static ports (VPCs to Legacy N6K-1 and N6K-2). MCP has been disabled for testing purposes regarding STP. 

When adding the VPC as static port from Pod 2 to the EPG the loop has been built. Technically correct, but the STP mechanism won't do anything to prevent the loop.

It's not an option to remove the corresponding VLAN from the interconnects between N6K and N5K for redundancy reasons.

The question is: Would MCP do it or is there any different way for a full redundancy if one N6K becomes unavailable?

Thank you very much Cisco Community.

Danny

[balaji.bandi]

If you are migrating Classic Ethernet to Fabric. 

So my suggestion is to extend the VLAN across the Fabric, and you only choose one of  the patches and allow the VLAN to reach the Fabric (can you also keep the configuration on the other side, in case a disaster happens, to bring the Layer 2 connection on the other side of the network)

N6K1 to POD1 for all VLANs allowed 

That means all the traffic goes via POD1 until the Migration is finished.

If you like to use both PODs, then only allow the VLAN on the respective POD.

Example :

N6K1 to POD1 - even VLAN

N6K2 to POD3 - Odd  VLAN

I hope this makes sense to you. Once all migrations are complete, you can remove the Nexus Classic environment anyway.

[hrtendrup]

Remember that ACI does not participate in STP. Your port type on the 6ks probably should be shared, not point-to-point. The port then has to transition through the listen phase of STP before forwarding. That should be enough time for STP to propagate through ACI and one of the portchannels on the 6ks should move to blocking.

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