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Catalyst 3560 Switch Software Configuration Guide
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Chapter 40 Configuring HSRP
Configuring HSRP
Enabling HSRP Support for ICMP Redirect Messages
In releases earlier than Cisco IOS Release 12.2(18)SE, ICMP (Internet Control Message Protocol)
redirect messages were automatically disabled on interfaces configured with HSRP. ICMP is a network
layer Internet protocol that provides message packets to report errors and other information relevant to
IP processi ng. ICMP prov ides diagnostic functions, such as s ending and directing error packets to the host.
When the switch is running HSRP, make sure hosts do not discover the interface (or real) MAC addresses
of routers in the HSRP group. If a host is redirected by ICMP to the real MAC address of a router and
that router later fails, packets from the host will be lost.
In Cisco IOS Release 12.2(18)SE and later, ICMP redirect messages are automatically enabled on
interfaces configured with HSRP. This feature filters outgoing ICMP redirect messages through HSRP,
in which the next hop IP address might be changed to an HSRP virtual IP address. For more information,
see the Cisco IOS IP Configuration Guide, Release 12.2.
Configuring HSRP Groups and Clustering
When a device is participating in an HSRP standby routing and clustering is enabled, you can use the
same standby group for command switch redundancy and HSRP redundancy. Use the cluster
standby-group HSRP-group-name [routing-redundancy] global configuration command to enable the
same HSRP standby group to be used for command switch and routing redundancy. If you create a cluster
with the same HSRP standby group name without entering the routing-redundancy keyword, HSRP
standby routing is disabled for the group.
This example shows how to bind standby group my_hsrp to the cluster and enable the same HSRP group
to be used for command switch redundancy and router redundancy. The command can only be executed
on the cluster command switch. If the standby group name or number does not exist, or if the switch is
a cluster member switch, an error message appears.
Switch# configure terminal
Switch(config)# cluster standby-group my_hsrp routing-redundancy
Switch(config)# end
Troubleshooting HSRP
If one of the situations in Tabl e 40-2 occurs, this message appears:
%FHRP group not consistent with already configured groups on the switch stack -
virtual MAC reservation failed
Tab l e 40-2 Troubleshooting HSRP
Situation Action
You configure more than 32 HSRP group
instances.
Remove HSRP groups so that up to 32 group
instances are configured.
You configure HSRP for IPv4 and HSRP for IPv6
at the same time
Configure either HSRP for IPv4 or HSRP for IPv6
on the switch.
You configure group numbers that are not in valid
ranges of 256.
Configure group numbers in a valid range.