In the hardware address 0000.0c07.ac0a, what does 07.ac represent?

A.
HSRP well-known physical MAC address

B.
Vendor code

C.
HSRP router number

D.
HSRP group number

E.
HSRP well-known virtual MAC address

Explanation:

HSRP code (HSRP well-known virtual MAC address) – The fact that the MAC address is for an HSRP virtual router is indicated in the next two bytes of the address. The HSRP code is always 07.ac. The HSRP protocol uses a virtual MAC address, which always contains the 07.ac numerical value.
Reference: Building Cisco Multilayer Switched Networks (Cisco Press) page 268