Active/standby question

yes, it is connection mirroring.

sol13478: Overview of connection and persistence mirroring (11.x)

when using connection mirror, ingress traffic can be seen on standby unit.

Packets on the active BIG-IP that require mirroring are transmitted to the standby unit. The standby unit then processes the traffic through the inbound side of the TCP stack and hands it off to TMM as if it were the active unit. However, the output stack is disconnected, and no trafffic is actually sent on the wire. This process allows the standby unit to maintain full state information for the mirrored connections in order to fail over seamlessly.

sol9701: The tcpdump utility with a VLAN filter on the standby unit may capture load-balanced traffic