Why is a digital MAC tackle wanted in FHRP protocols?


In RFC 5798 which defines the operations of VRRP, you’ll find in part 7.3 the next:
(emphasis mine)

7.3. Digital Router MAC Tackle

The digital router MAC tackle related to a digital router is
an IEEE 802 MAC Tackle within the following format:

IPv4 case: 00-00-5E-00-01-{VRID} (in hex, in Web-standard bit-
order)

The primary three octets are derived from the IANA’s Organizational
Distinctive Identifier (OUI). The following two octets (00-01) point out the
tackle block assigned to the VRRP
for IPv4 protocol. {VRID} is the
VRRP Digital Router Identifier
. This mapping offers for as much as 255
IPv4 VRRP routers on a community.

IPv6 case: 00-00-5E-00-02-{VRID} (in hex, in Web-standard bit-
order)

The primary three octets are derived from the IANA’s OUI. The following
two octets (00-02) point out the tackle block assigned to the VRRP
for IPv6 protocol. {VRID} is the VRRP Digital Router Identifier.
This mapping offers for as much as 255 IPv6 VRRP routers on a community.

In order you’ll be able to see the mac tackle convey data, it inform the opposite gadgets that this can be a VRRP tackle and even present the VRID.

Additionally remember the fact that you’ll be able to outline a number of cases of digital gateway on the identical gadget, and whereas they might all use the identical mac tackle it’s cleaner to have separate mac-addresses.

The identical logic apply to HSRP (which, admittedly VRRP is derived from).



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