Multiple HSRP Groups

To load balance routers, assign them to multiple groups on the same subnet.

©2006 Cisco Systems, Inc. All rights reserved.

With a single HSRP group on a subnet, the active router is forwarding all the packets off that subnet while the standby router is forwarding no packets off that subnet. To facilitate load sharing, and hence have both routers load balancing, a single router may be a member of multiple HSRP groups that exist on the same segment.

Multiple standby groups further enable redundancy and load sharing within networks. While a router is actively forwarding traffic for one HSRP group, the router can be in standby or listen state for another group.

Each standby group emulates a single virtual router. There can be up to 255 standby groups on any LAN, but the maximum standby groups that are necessary should be no more than the number of active routers required. In most cases, the required number will be two.

Caution Increasing the number of groups in which a router participates increases the load on the router. This can have an impact on the performance of the router.

In the figure, both router A and router B are members of groups 1 and 2. However, router A is the active forwarding router for group 1 and the standby router for group 2. Router B is the active forwarding router for group 2 and the standby router for group 1.

5-36 Building Cisco Multilayer Switched Networks (BCMSN) v3.0

© 2006 Cisco Systems, Inc.

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