VRRP Introduction
©2008 Allied Telesis Inc. All rights reserved.
46.2
AlliedWare Plus
TM
Operating System Software Reference C613-50003-00 REV E
Software Version 5.2.1
Introduction
This chapter describes the Virtual Router Redundancy Protocol (VRRP) feature provided by
the switch, and how to configure the switch to participate in a virtual router.
One function of a switch 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 those on the WAN.
The Virtual Router Redundancy Protocol defined in RFC 2338 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 then operate together to provide a single logical gateway for
hosts on the LAN.