Avaya ERS 8600 series, Configuration Manual

Page: 63 / 420

VRRP advertisements and master router failover
When a VRRP router is initialized, if it is the IP address owner, its priority is 255 and it sends
a VRRP advertisement. The master router then continues to send advertisement messages
at the advertisement interval period.
The other VRRP routers transition to the backup state in the following situations:
• if the priority in the received advertisement is greater than the local priority
• if the priority in the received advertisement is the same as the local priority and the primary
IP address of the sender is greater than the local primary IP address
The backup routers use the advertisements from the master router as a keepalive to monitor
the health of the master router. If the backup router does not receive an advertisement during
the master downtime interval, calculated as 3 * advertisement interval, then the master router is
declared down.
If a shutdown occurs, the master router sends a VRRP advertisement with a priority of 0 and
transitions to the initialize state.
The priority value 0 indicates that the master router has stopped participating in VRRP. This
triggers the backup router to transition to the master state without waiting for the current master
to time out.
VRRP terms
The following terms are specific to VRRP:
• VRRP router—a router running the VRRP protocol
•
Virtual router—an abstract object acting as the default router for one or more hosts,
consisting of a virtual router ID and a set of addresses
• IP address owner—the VRRP router that has virtual router IP addresses as real interface
addresses (the router that responds to packets sent to this IP address.)
• Primary IP address—an IP address selected from the real addresses and used as the
source address of packets sent from the router interface (The virtual router master sends
VRRP advertisements using this IP address as the source.)
• Virtual router master—the router assuming responsibility for forwarding packets sent to
the IP address associated with the virtual router and answering ARP requests for these
IP addresses
• Virtual router backup—the virtual router that becomes the master router if the current
master router fails
IPv6 VRRP
Configuration — IPv6 Routing November 2010 63