Allied Telesis AT-S63 - Manual (Page 345)

AT-S63 Management Software Features Guide
Section VII: Routing 345
Overview
This chapter describes the Virtual Router Redundancy Protocol (VRRP)
support provided by the switch.
One of the functions performed by switches is to act as a gateway to the
WAN for hosts on a LAN. On larger LANs, two or more switches may act
as the gateway, and hosts use a dynamic routing protocol, such as RIP or
OSPF, to determine the gateway switch to use as the next hop in order to
reach a specific IP destination. However, there are a number of factors,
such as administrative or processing overhead, that may make it
undesirable to use a dynamic routing protocol. One alternative is to use
static routing. However, if the statically configured first hop switch fails, the
hosts on the LAN are unable to communicate with hosts on the WAN.
The Virtual Router Redundancy Protocol provides a solution to the
problem by combining two or more physical switches into a logical
grouping called a virtual router (VR). The physical switches in the virtual
router operate together to provide a single logical gateway for hosts on the
LAN.