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Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-09
Chapter 32 Configuring HSRP
Configuring HSRP
Configuring HSRP Authentication and Timers
You can optionally configure an HSRP authentication string or change the hello-time interval and
holdtime.
When configuring these attributes, follow these guidelines:
• The authentication string is sent unencrypted in all HSRP messages. You must configure the same
authentication string on all routers and access servers on a cable to ensure interoperation.
Authentication mismatch prevents a device from learning the designated Hot Standby IP address and
timer values from other routers configured with HSRP.
• Routers or access servers on which standby timer values are not configured can learn timer values
from the active or standby router. The timers configured on an active router always override any
other timer settings.
• All routers in a Hot Standby group should use the same timer values. Normally, the holdtime is
greater than or equal to 3 times the hellotime.
Beginning in privileged EXEC mode, use one or more of these steps to configure HSRP authentication
and timers on an interface:
Use the no standby [group-number] authentication string interface configuration command to delete
an authentication string. Use the no standby [group-number] timers hellotime holdtime interface
configuration command to restore timers to their default values.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and enter the HSRP
interface on which you want to set authentication.
Step 3
standby [group-number] authentication string (Optional) authentication string—Enter a string to be carried in
all HSRP messages. The authentication string can be up to eight
characters in length; the default string is cisco.
(Optional) group-number—The group number to which the
command applies.
Step 4
standby [group-number] timers hellotime
holdtime
(Optional) Configure the time between hello packets and the
time before other routers declare the active router to be down.
• group-number—The group number to which the command
applies.
• hellotime—The hello interval in seconds. The range is from
1 to 255; the default is 3 seconds.
• holdtime—The time in seconds before the active or standby
router is declared to be down. The range is from 1 to 255;
the default is 10 seconds.
Step 5
end Return to privileged EXEC mode.
Step 6
show running-config Verify the configuration of the standby groups.
Step 7
copy running-config startup-config (Optional) Save your entries in the configuration file.
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