Yes, you can add a direct back-to-back connection between remote leaf switches in a vPC pair, but it needs to be done carefully to avoid traffic disruption. Since your setup currently runs without a B2B link, introducing one changes how vPC synchronization happens, as it will now happen directly instead of via the spine.
To implement this, you simply connect the interfaces between the remote leafs and ensure the ports are configured correctly. The fabric will detect the new peer link automatically if everything is set properly. As long as the vPC consistency is maintained and there are no flaps or misconfigurations, traffic should continue without interruption.
However, to be safe, do it during a maintenance window. Monitor vPC health and ensure both leaves are running compatible firmware. This is a supported change in ACI, but there’s no official step-by-step guide for adding B2B links after deployment. If needed, reach out to Cisco TAC for version-specific guidance.
