http://datatracker.ietf.org/doc/rfc5798/?include_text=1
7.3. Virtual Router MAC Address
The virtual router MAC address associated with a virtual router is an
IEEE 802 MAC Address in the following format:
IPv4 case: 00-00-5E-00-01-{VRID} (in hex, in Internet-standard bit-
order)
The first three octets are derived from the IANA's Organizational
Unique Identifier (OUI). The next two octets (00-01) indicate the
address block assigned to the VRRP for IPv4 protocol. {VRID} is the
VRRP Virtual Router Identifier. This mapping provides for up to 255
IPv4 VRRP routers on a network.
IPv6 case: 00-00-5E-00-02-{VRID} (in hex, in Internet-standard bit-
order)
The first three octets are derived from the IANA's OUI. The next two
octets (00-02) indicate the address block assigned to the VRRP for
IPv6 protocol. {VRID} is the VRRP Virtual Router Identifier. This
mapping provides for up to 255 IPv6 VRRP routers on a network.