Specifications

CHAPTER 6

First Hop Redundancy

Configuring HSRP

To begin configuring HSRP, use the standby group-number ip virtual-IP-address command in interface configuration

mode. Routers in the same HSRP group must belong to the same subnet/virtual LAN (VLAN.) Give this command under

the interface connecting to that subnet or VLAN. For instance, use the following to configure the router as a member of

HSRP group 39 with virtual router IP address 10.0.0.1:

Router(config-if)# standby 39 ip 10.0.0.1

HSRP authentication helps prevent unauthorized routers from seeing user traffic:

Router(config-if)# stand 2 authentication md5 key-string cisco

Tune HSRP with four options: Priority, Preempt, Timers, and Interface Tracking.

Manually select the active router by configuring its priority higher than the default of 100:

Router(config-if)# standby 39 priority 150

Along with configuring priority, configure preempt to enable a router to take over if the active router has lower priority,

as shown in the following commands. This helps lead to a predictable data path through the network. The second

command shown delays preemption until the router or switch has fully booted and the routing protocol has converged.

Time how long it takes to boot and add 50 percent to get the delay value in seconds:

Router(config-if)# standby 39 preempt

Router(config-if)# standby 39 preempt delay minimum 90

Speed convergence by changing the hello and hold times. The following sets the hello interval to 1 second and the hold

time to 3 seconds. They can be set between 1–255 seconds (the default hello is 3 seconds and hold time is 10 seconds):

Router(config-if)# standby 39 timers 1 3

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CCNP SWITCH 642-813 Quick Reference by Denise Donohue

9781587140112.qxd 11/23/09 11:35 AM Page 74