Hi, This question never comes to my mind but here is what I can tell you on CARP in fail-over mode. The switch is not seeing the same "virtual" MAC address on two ports, it using only seeing "virtual" MAC address moving from one port to another when a failover occurs.
CARP is done trough Virtual Router Redundancy Protocol (multicast advertising) see http://en.wikipedia.org/wiki/VRRP for some deeper explanation. carp(4) also contains interesting information. Hope this helps, Benjamin Constant The information contained in this transmission may contain privileged and confidential information. It is intended only for the use of the person(s) named above. If you are not the intended recipient, you are hereby notified that any review, dissemination, distribution or duplication of this communication is strictly prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy all copies of the original message. This communication is from TI Automotive.
