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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Configuring HSRP and VRRP
Configuring HSRP
Configuring MHSRP
To enable MHSRP and load-balancing, you configure two routers as active routers for their groups, with
virtual routers as standby routers. This example shows how to enable the MHSRP configuration shown
in Figure 1-2. You need to enter the standby preempt interface configuration command on each HSRP
interface so that if a router fails and comes back up, the preemption occurs and restores load-balancing.
Router A is configured as the active router for group 1, and Router B is configured as the active router
for group 2. The HSRP interface for Router A has an IP address of 10.0.0.1 with a group 1 standby
priority of 110 (the default is 100). The HSRP interface for Router B has an IP address of 10.0.0.2 with
a group 2 standby priority of 110.
Group 1 uses a virtual IP address of 10.0.0.3 and group 2 uses a virtual IP address of 10.0.0.4.
Router A Configuration
Switch# configure terminal
Switch(config)# interface gigabitethernet1/0/1
Switch(config-if)# no switchport
Switch(config-if)# ip address 10.0.0.1 255.255.255.0
Switch(config-if)# standby 1 ip 10.0.0.3
Switch(config-if)# standby 1 priority 110
Switch(config-if)# standby 1 preempt
Switch(config-if)# standby 2 ip 10.0.0.4
Switch(config-if)# standby 2 preempt
Switch(config-if)# end
Router B Configuration
Switch# configure terminal
Switch(config)# interface gigabitethernet1/0/1
Switch(config-if)# no switchport
Switch(config-if)# ip address 10.0.0.2 255.255.255.0
Switch(config-if)# standby 1 ip 10.0.0.3
Switch(config-if)# standby 1 preempt
Switch(config-if)# standby 2 ip 10.0.0.4
Switch(config-if)# standby 2 priority 110
Switch(config-if)# standby 2 preempt
Switch(config-if)# end
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.
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