Redundancy; Virtual Router Redundancy Protocol (Vrrp); Simple Router Redundancy Protocol (Srrp) - Avaya P333R User Manual

Chapter 1 Overview

Redundancy

Routing protocols naturally provide some level of redundancy. However, IP
stations that are manually configured with a single 'default gateway' IP address do
not naturally recover when their default gateway fails. These stations do not
automatically try to use other routers or Layer-3-switches connected to the same
subnet.
The P333R supports two router redundancy protocols, VRRP and SRRP, to solve
this problem.

Virtual Router Redundancy Protocol (VRRP)

VRRP is an IETF protocol designed to support redundancy of routers on the LAN,
as well as load balancing of traffic. VRRP is transparent to host stations, making it
an ideal choice when redundancy, load balancing and ease of configuration are all
required.
The concept underlying VRRP is that a router can backup other routers, in addition
to performing its primary routing functions. This redundancy is achieved by
introducing the concept of a virtual router. A virtual router is a routing entity
associated with multiple physical routers. The routing functions of the virtual router
are performed by one of the physical routers with which it is associated. This router
is known as the master router.
For each virtual router, VRRP selects a master router. If the selected master router
fails, another router is selected as master router.
In VRRP, two or more physical routers can be associated with a virtual router, thus
achieving the extreme reliability inherent in the P333R SAFER architecture.
In a VRRP environment, host stations interact with the virtual router. They are not
aware that this router is a virtual router, and they are not affected when a new
router takes over the role of master router. This makes VRRP fully interoperable
with every host station.
VRRP can be activated on an interface using a single command while allowing for
the necessary fine-tuning of the many VRRP parameters. For a detailed description
of VRRP, refer to VRRP standards and published literature.

Simple Router Redundancy Protocol (SRRP)

Avaya P333R IP SRRP redundancy capabilities provide automatic backup Layer 3
switching for IP stations. P333R units can be configured to back each other up so
that if one fails the other will take over its forwarding functions. The backup P333R
is not idle. As long as both P333R units are functional, traffic is shared between
them. The P333R modules can be in the same Avaya P330 stack or in different,
connected, Avaya P330 stacks. The P333R can back up another P333R unit or any
other router.
8 Avaya P333R User's Guide