1) The system with the lower MAC address wins as master and this election is not governed by the vPC role priority 2) Before you introduce an already isolated vPC device back into production, check the LACP roles on both boxes. If the same role, disable auto recovery with no auto-recovery under the vPC domain on both peers and reload the isolated device. After reload, the isolated device comes up with the LACP role 'none established' and can be introduced into the vPC without LACP role re- election. Reference: https://www.cisco.com/c/en/us/support/docs/interfaces-modules/nexus-7000-series-supervisor-1- module/119033-technote-nexus-00.html