Symptom

Traffic across peer-link is not sent correctly resulting in traffic loss. Control-plane protocols like HSRP may get out-of-sync. mac-address not synced correctly between the vPC peers. Good side: N7K-B#show system internal l2fm info detail Peer link: Po1 mct_vlan_bmp 108,113,118,121-122,157,163,173,178,188,191,193-194 Broken side: N7K-A#show system internal l2fm info detail Peer link: Po1 mct_vlan_bmp 108,113,118,121-122,157,173,178,188,191,193-194 <<== Vlan 163 missing

Conditions

This issue is seen in Nexus7000 vPC setup running 6.2.x releases AND vPC peers has vPC ports in access mode. This issue occurs when vPC access ports and vPC peer-links come up at the same time.

Workaround

Configure vPC ports as trunks instead of access ports, to avoid this issue. If the issue has occurred and to recover from the situation: Flap the peer-link on the Nexus7000 that has bad state. Please be aware that flapping peer-link could be very intrusive.

Further Problem Description