Defined in RFC 2281, HSRP is a Cisco-proprietary protocol in

Defined in RFC 2281, HSRP is a Cisco-proprietary protocol in which routers are put into an HSRP router group. Along with dynamic routing protocols and STP, HSRP is regarded as a high-availability network service, since all 3 have an nearly instant cutover to a secondary path once the main path is unavailable.

One from the routers will be selected because the main ("Active", in HSRP terminology), and that primary will deal with the routing whilst the other routers are in standby, prepared to handle the load when the primary router becomes unavailable. Within this fashion, HSRP guarantees a higher network uptime, because it routes IP visitors without relying on a single router.

The hosts using HSRP as a gateway do not know the actual IP or MAC addresses of the routers within the group. They're communicating having a pseudorouter, a "virtual router" produced from the HSRP configuration. This virtual router will have a virtual MAC and IP adddress also.

The standby routers aren't just going to become sitting there, though! By configuring multiple HSRP groups on a single interface, HSRP load balancing can be achieved.

Before we get to the more advanced HSRP configuration, we better get a fundamental one started! We'll be using a two-router topology right here, and keep in mind that 1 or each of those routers might be multilayer switches also. For ease of reading, I'm going to refer to them only as routers.

R2 and R3 will both be configured to become in standby group five. The virtual router will have an IP address of 172.12.23.ten /24. All hosts in VLAN 100 should use this address as their default gateway.

R2(config)#interface ethernet0

R2(config-if)#standby five ip 172.12.23.ten

R3(config)#interface ethernet0

R3(config-if)#standby 5 ip 172.12.23.ten

The show command for HSRP is show standby, and it's the first command you should run while configuring and troubleshooting HSRP. Let's run it on both routers and evaluate results.

R2#show standby

Ethernet0 - Group five

Local state is Standby, priority one hundred

Hellotime three sec, holdtime 10 sec

Next hello sent in 0.776

Virtual IP address is 172.12.23.ten configured

Active router is 172.12.23.3, priority one hundred expires in 9.568

Standby router is local

1 state modifications, final state alter 00:00:22

R3#show standby

Ethernet0 - Group five

Local state is Active, priority one hundred

Hellotime 3 sec, holdtime 10 sec

Subsequent hello sent in two.592

Virtual IP address is 172.12.23.ten configured

Active router is local

Standby router is 172.12.23.two expires in 8.020

Virtual mac address is 0000.0c07.ac05

2 state modifications, last state change 00:02:08

We can see that R3 has been chosen as the Active router ("local state is Active"), the virtual router's IP is 172.12.23.10, and R2 is the standby router.

You will find some HSRP values that you'll have to change from time to time. What if we want R2 to become the Active router rather? Can we alter the MAC address of the virtual router? I'll answer those concerns in the next a part of this HSRP tutorial!

View this post on my blog: http://www.timer-relay.com/automation/defined-in-rfc-2281-hsrp-is-a-cisco-proprietary-protocol-in.html