Nortel Networks WEB OS 212777 - Manual (Page 256)

Web OS 10.0 Application Guide
256 n Chapter 11: High Availability
212777-A, February 2002
Hot-Standby Redundancy
In a hot-standby configuration, Spanning Tree Protocol (STP) is not needed to eliminate bridge
loops. This speeds up failover when a switch fails. The standby switch blocks all ports configured
as standby ports, whereas the master switch enables these same ports. Consequently, on a given
switch, all virtual routers are either master or backup; they cannot change state individually.
To provide as much flexibility as possible, the old hot-standby approach has been modified to
eliminate the problems previously associated with it and is now based on VRRP. In a hot-standby
configuration, two or more switches provide redundancy for each other. One switch is elected
master and actively processes Layer 4 traffic. The other switches (the backups) assume the master
role should the master fail. The backups may forward Layer 2 and Layer 3 traffic as appropriate.
There are three components to the VRRP-based, hot-standby model: the virtual router group,
additional Layer 4 port states, and configuration synchronization options. The hot-standby
model is shown in
Figure 11-6 .
Figure 11-6 Hot-Standby Redundancy
Internet
Router
Router
Active VIP 1
VIP: 205.178.13.226
Standby VIP 1
VIP: 205.178.13.226
Active VIP 2
VIP: 205.178.13.240
Standby VIP 2
VIP: 205.178.13.240
Active VIP 3
VIP: 205.178.13.110
Standby VIP 3
VIP: 205.178.13.110
Active
Hot Standby