Enabling Hsrp Support For Icmp Redirect Messages; Displaying Hsrp Configurations - Cisco WS-C3020 Software Configuration Manual

Chapter 38 Configuring HSRP and Enhanced Object Tracking

Enabling HSRP Support for ICMP Redirect Messages

ICMP (Internet Control Message Protocol) 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.
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.

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.
This is a an example of output from the show standby privileged EXEC command, displaying HSRP
information for two standby groups (group 1 and group 100):
Switch# show standby
VLAN1 - Group 1
Local state is Standby, priority 105, may preempt
Hellotime 3 holdtime 10
Next hello sent in 00:00:02.182
Hot standby IP address is 172.20.128.3 configured
Active router is 172.20.128.1 expires in 00:00:09
Standby router is local
Standby virtual mac address is 0000.0c07.ac01
Name is bbb
VLAN1 - Group 100
Local state is Active, priority 105, may preempt
Hellotime 3 holdtime 10
Next hello sent in 00:00:02.262
Hot standby IP address is 172.20.138.51 configured
Active router is local
Standby router is unknown expired
Standby virtual mac address is 0000.0c07.ac64
Name is test
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Cisco Catalyst Blade Switch 3020 for HP Software Configuration Guide
Displaying HSRP Configurations
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