To enable both VRRP switches to route traffic, the switch software has an extension to VRRP, the BackupMaster, that creates an active-active environment for routing. If you enable BackupMaster on the backup router, the backup router no longer switches traffic to the VRRP Master. Instead the BackupMaster routes all traffic received on the BackupMaster IP interface according to the switch routing table.
Stagger VRRP instances on a network or subnet basis.
The following figure shows the VRRP Masters and BackupMasters for two subnets.
The VRRP BackupMaster uses the VRRP standardized backup switch state machine. Thus, VRRP BackupMaster is compatible with standard VRRP.
For VOSS 7.1 releases and later, the handling of IPv4 Layer 2 unicast packets (for example, ARP Request/Reply) with the destination MAC as VRRP MAC has been modified on BackupMaster. These packets are now handled by VRRP Master only.
The BackupMaster forwards all IPv4 Layer 2 unicast packets to the Master and the Master VRRP sends an ARP reply only.
Processing of IP unicast packets (for example, ICMP packets to VRRP IP) or IPv4 routed packets (with destination MAC as VRRP MAC) on VRRP BackupMaster stays the same. For example, the VRRP BackupMaster replies to ICMP requests and routes Layer 3 routed packets to the destination and does not forward these packets to the Master when they arrive at the BackupMaster.
To reflect these changes, the VRRP MAC entry on the BackupMaster points to the Master instead of itself, and the ARP entry for VRRP IP on the the BackupMaster points to local.