Q. What is the standby use-bia command and how does it work?
A. By default, HSRP uses the preassigned HSRP virtual MAC address <...> In order to configure HSRP to use the burnt-in address of the interface as its virtual MAC address, instead of the default, use the standby use-biacommand.
Note: Using thestandby use-biacommand has these disadvantages:
When a router becomes active the virtual IP address is moved to a different MAC address. The newly active router sends a gratuitous ARP response, but not all host implementations handle the gratuitous ARP correctly.
Proxy ARP breaks when use-bia is configured. A standby router cannot cover for the lost proxy ARP database of the failed router.