Two vPC pairs, four management ports of Nexus 5k, are connected to a vlan on a Catalyst switch, and the vPC Peer-Keepalive is performed on the ports. Should I give a different vPC domain id for every pair?
Thank you for your cooperation in advance.
The answer is Yes.
Each vpc cluster (not depending on which nexuses it's built 5k or 7k) has to have unique vpc domain name. Ther reason is that botn peers in the domain create vistual MAC address and use it as ID for all VPC LACP port-channels.
And if you will try to interconnect two clusters with such links there will be a conflict of ID's which will cause instability.