Assuming that the “A” Fabric Interconnect indeed has failed, the appliance port on A will also be down. The vNIC will failover to B (assuming failover is configured, as per your comment). Now, we have to look at what your blade is trying to do. If it’s pure L2, trying to reach the MAC address of the port connected to the now-failed Fabric A, the traffic will be received by FI-B, and since that MAC address is unknown to that FI, will be sent out the uplink port. The upstream L2 environment, having no path to the MAC address (since FI-A is down), will flood the frame out all ports except the ingress (that came from FI-B). In any case, that MAC address is no longer accessible and the frame will eventually be dropped by all node ports.

If you’re running something L3 (iSCSI or NFS for example), the Ethernet frame generated will still be targeted for the old MAC address, at least until your IP stack decides to age out the ARP entry. Once that happens, a new ARP request will be sent, at which point the MAC address on the FI-B appliance interface will be learned *assuming that your appliance has also failed the IP address over to the other port*. Traffic can then be switched locally in FI-B, and no trip to the uplink port is required.

A better solution (assuming L3) would be to have an IP address on each of the two appliance interfaces (one for A, one for B), and have your application/initiator/etc addressing both – fabric failover doesn’t really come into play here (though it could). When FI-A goes down, that path and IP would get marked unreachable, and you’d begin (or continue, assuming active/active configration) using the interface on FI-B – again, switched locally and not having to go to the upstream L2 environment.

Never seen this myself – anyone else?

- Dave

topology is nexus 7K with port-chan’s to the a and b side..6120 is in EH mode..the port-chan’s going to gateway 2 fail the dhcp boot request..