Primary Address; Virtual Router Master - Alcatel-Lucent 7705 Configuration Manual

VRRP Components

Primary Address

A primary address is an IP address selected from the set of real interface addresses. VRRP
advertisements are always sent using the primary IP address as the source of the IP packet.
A 7705 SAR IP interface must always have a primary IP address assigned for VRRP to be
active on the interface. The 7705 SAR supports primary addresses and multi-netting on the
IP interface. The virtual router VRID primary IP address is always the same as the primary
address on the IP interface.

Virtual Router Master

The physical router that is participating in VRRP and which controls the IP address(es)
associated with the virtual router is called the master. The virtual router master is always the
IP address owner as long as it is available. The master is responsible for forwarding packets
sent to the VRRP IP addresses. An election process provides dynamic failover of the
forwarding responsibility to the backup router if the master becomes unavailable. This allows
any of the virtual router IP addresses on the LAN to be used as the default first-hop router by
end hosts. VRRP enables a higher-availability default path without requiring configuration of
dynamic routing or router discovery protocols on every end host.
If the master is unavailable, each virtual router backup with the same VRID compares its
configured priority values to determine the master role. In case of a tie, the virtual router with
the highest primary IP address becomes the master.
The preempt parameter is supported and can be set to false to prevent a backup router
that has a higher priority value from becoming master if an existing non-owner virtual router
is the current master. Preemption assures that the preferred router will regain its master status
when service restoration occurs and it goes back on line. Preemption can be enabled or
disabled.
While master, a virtual router routes and originates all IP packets into the LAN using the
physical MAC address for the IP interface as the Layer 2 source MAC address, not the VRID
MAC address. ARP packets also use the parent IP interface MAC address as the Layer 2
source MAC address while inserting the virtual router MAC address in the appropriate
hardware address field. VRRP messages are the only packets transmitted using the virtual
router MAC address as the Layer 2 source MAC address.
A new virtual router master is selected from the set of VRRP routers available to assume
forwarding responsibility for a virtual router if the current master fails.
214 7705 SAR OS Router Configuration Guide