Enabling Hsrp Support For Icmp Redirect Messages; Configuring Hsrp Groups And Clustering; Displaying Hsrp Configurations - Cisco 3750G - Catalyst Integrated Wireless LAN Controller Configuration Manual

Chapter 39 Configuring HSRP and Enhanced Object Tracking

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 processing. ICMP provides diagnostic functions, such as sending 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

Displaying HSRP Configurations

From privileged EXEC mode, use this command to display HSRP settings:
show standby [interface-id [group]] [brief] [detail]
You can display HSRP information for the whole switch, for a specific interface, for an HSRP group, or
for an HSRP group on an interface. You can also specify whether to display a concise overview of HSRP
information or detailed HSRP information. The default display is detail. If there are a large number of
HSRP groups, using the show standby command without qualifiers can result in an unwieldy display.
OL-8550-02
Displaying HSRP Configurations
Catalyst 3750 Switch Software Configuration Guide
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