Symptom

Nexus 93xx or 95xx vPC pair (local or across OTV) with 4-way HSRP configured can see traffic loss. This is because a Nexus 9K switch in HSRP "Listen" state has the virtual gateway MAC address programmed in "my_station_tcam". To the switch, this indicates that the switch "owns" or is the "gateway" for the vMAC, and the switch will route the traffic, potenially to the wrong interface and next-hop.

Conditions

- Nexus 93xx and/or 95xx in back-to-back vPC (or L2-adajcent) - Running 7.0(3)I6(1), 7.0(3)I7(1), or 7.0(3)I7(2) - 3- or 4-way HSRP configured

Workaround

- In some cases a shut / no shut of the SVI can reprogram things correctly. - There are also some cases where configuring a static mac address for the virtual MAC, then removing the static entry can reprogram this state correctly. - Finally, shutting the SVI on the switches that are in an HSRP "Listen" or "Backup" state definitely resolves the issue.

Further Problem Description