Nortel Networks WEB OS 212777 - Manual (Page 275)

Web OS 10.0 Application Guide
Chapter 11: High Availability n 275
212777-A, February 2002
VRRP-Based Hot-Standby Configuration
A hot-standby configuration allows all processes to failover to a backup switch if any type of
failure should occur. The primary application for hot-standby redundancy is to avoid bridging
loops when using the Spanning Tree Protocol (STP), IEEE 802.1d. VRRP-based hot-standby
supports the default Spanning Tree only. It does not support multiple Spanning Trees.
Figure 11-10 shows a classic network topology, designed with redundancy in mind. This topol-
ogy contains bridging loops that would require the use of STP. In the typical network, STP
failover time is 45-50 seconds, much longer than the typical failover rate using VRRP only.
N OTE – To use hot-standby redundancy, peer switches must have an equal number of ports.
Figure 11-10 Hot-Standby Configuration
N OTE – In complex networks, STP convergence time can be much higher than 45-50 seconds.
If VRRP was used in this configuration, it would require STP. An important factor to consider is
that the switch would be affected by the slower failover time of STP even if VRRP were in use.
While VRRP can be used without STP in this scenario, doing so would involve a more com-
plex network configuration, requiring multiple subnets and/or VLANs and enabling IP for-
warding to route between them.
Legend
1. L4 ports are configured as Hot-Standby.
2. Crosslink is configured as Interswitch link.
Active
Side
Servers
C H C H
Hub
7
Clients
7
1 S H
3 3
Interswitch link
Standby
Side
Hub
S H
1