HP 3500YL - Manual (Page 333)

Virtual Router Redundancy Protocol (VRRP)
Overview
L i c e n s e
R e q u i r e m e n t s
Overview
In many networks, edge devices are often configured to send packets to a
statically configured default router. If this router becomes unavailable, the
devices that use it as their first-hop router become isolated from the network.
VRRP uses dynamic failover to ensure the availability of an end node’s default
router. This is done by assigning the IP address used as the default route to a
“virtual router”, or VR. The VR includes:
■ an Owner router assigned to forward traffic designated for the virtual
router (If the Owner is forwarding traffic for the VR, it is the Master
router for that VR.)
■ one or more prioritized Backup routers (If a Backup is forwarding traffic
for the VR, it has replaced the Owner as the Master router for that VR.)
In the 3500yl, 5400zl, and 6600 switches, VRRP is included with the Premium
License. In the 6200yl and 8200zl switches, this feature is included with the base
feature set.
This redundancy provides a backup for gateway IP addresses (first- hop
routers) so that if a VR’s Master router becomes unavailable, the traffic it
supports will be transferred to a Backup router without major delays or
operator intervention.This operation can eliminate single-point-of-failure
problems and provide dynamic failover (and failback) support. As long as one
physical router in a VR configuration is available, the IP addresses assigned
to the VR are always available, and the edge devices can send packets to these
IP addresses without interruption.
Advantages to using VRRP include:
■ minimizing failover time and bandwidth overhead if a primary router
becomes unavailable
■ minimizing service disruptions during a failover
■ providing backup for a load-balanced routing solution
■ addressing failover problems at the router level instead of on the
network edge
■ avoiding the need to make configuration changes in the end nodes if
a gateway router fails
■ eliminating the need for router discovery protocols to support failover
operation.
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