Virtual vs. Physical MAC Addresses Explained

This article explains the difference between virtual and physical MAC addresses.

Virtual MAC Address

• The virtual MAC address is associated with a virtual router.
• It’s an IEEE 802 MAC address, 48 bits in size.
• It’s specified in RFC3768 and RFC5768.
• The hexadecimal format for a virtual MAC address is: 00-00-5E-00-01-{VRID}
  • The first 3 octets are derived from the IANA OUI (Organizationally Unique Identifier).
  • The next 2 octets, 00 followed by 01, indicate the address block assigned to the VRRP (Virtual Router Redundancy Protocol).
  • {VRID} is the VRRP Virtual Router Identifier. Due to the 8-bit VRID field, up to 255 VRRP routers are supported in a network.

The virtual MAC address is associated with a VRRP virtual router, and the ARP (Address Resolution Protocol) converts IPv4 or IPv6 addresses into the virtual MAC address. The master router uses the virtual MAC address as the source address in all VRRP periodic messages.

Refer to the VRRP protocol documentation for more information.

Physical MAC Address

A physical MAC address is also 48 bits in size and consists of 6 hexadecimal digits.

Example: 00-14-2A-3F-47-D0

• The first 3 digits (00-14-2A in the example) represent the manufacturer.
• The last 3 digits represent a card- or device-specific unique number.