ETIC SIG, User Manual, Page: 44 / 83

CONFIGURATION
Page 44
User’s guide ref 9017409-01 SIG Router & VPN server
10 VRRP redundancy
10.1 Principle
VRRP is a protocol designed to increase the availability of the default
gateway of a subnet.
Thanks to VRRP, a group of two or more routers can service the hosts of
one subnet instead of only one usually; only one router of that group
actually routes frames; if it fails another one of the group takes its place.
The routers belonging to a VRRP group must be connected to the same
Ethernet segment.
VRRP works as follows :
An usual IP address is assigned to each router of the group.
An additional and common IP address, called the virtual IP address is
assigned to all the routers of the group. This virtual address is the address
which must be stored as the default gateway address in all the host
devices belonging to the subnet.
A priority index is assigned to each router of the group. Using that index,
the routers of the group can elect a master router; the master router is the
one which has the greatest priority code. The other routers are the backup
routers.
The master router is the only one to answer to the ARP requests and
route actually frames. It uses the virtual IP address and the virtual MAC
address If that option has been selected.
In case of failure of the master router, another master router is elected. It
replaces the router in failure. It will use the same virtual IP address and
the virtual MAC address as the previous master router.
The SIG router manages that protocol as well on the LAN and on the
WAN interface.