HSRP Notes

For me, Hot Standby Routing Protocol (HSRP) is very easy to configure and remember. For some reason, I have never forgotten how to configure it since the first time I have read about this technology.

HSRP tries to provide a virtual IP address in order to offer a First Hop Redundancy (Virtual Router Redundancy Protocol -VRRP is the open standard from IETF)

HSRP routers use the multicast addresses 224.0.0.2 (v1) and 224.0.0.102 (v2) to communicate between them. 

0000.0c07.acXX is the virtual Mac address of a HSRP router and XX is the HSRP group number.

rter#conf t
rter(conf)#interface fa0/0
rter(conf)#standby 1 ip 192.168.100.1 // instructs the router to use the virtual IP 192.168.100.1
rter(conf)#standby 1 priority 150 // sets the priority of this HSRP group to 150 (the highest being the highest priority)
rter(conf)#standby 1 preempt delay 2 // allows the router to switch automatically to the active state after 2 seconds if he has the highest priority
rter(conf)#standby 1 track s0/0 25 // the router will decrease its priority level by 25 if the s0/0 interface goes down
rter(conf)#standby 1 timers 4 10 // adjusts the timers
rter(conf)#standby 1 authentication md5 key-chain roadexpert // sets roadexpert as the md5 authentication key-chain for this HSRP group

Do not forget the option “use-bia” (use Burn In Address); this option can be very cute in the case of switchport security