Hi Networker,
Sorry it's called vpc peer-gateway. Cisco defines it as the following
"PC peer-gateway functionality allows a vPC switch to act as the active gateway for packets that are addressed to the router MAC address of the vPC peer. This feature enables local forwarding of such packets without the need to cross the vPC peer-link. In this scenario, the feature optimizes use of the peer-link and avoids potential traffic loss."
The thing is that VPC uses virtual mac-addresses and the F5 is most likely responding to the VPC peer-link mac-address instead of the mac-address that is embedded in the packet. I suspect that you are running into this issue.
You would find it in your VPC Domain statement
Bhattman