HSRP tracking

[Amafsha1]

Hello folks,  I’m having a difficult time finding an article that explains the tracking of an interface from HSRP standpoint in more depth.   Let’s say the interface  line protocol goes down, but the interface is still in an up state….so it would be up/down I guess.  Does that mean that HSRP sees this interface as down?  Or does the interface need to go to a full down/down state in order for the tracking to take over and HSRP to failover.  

[luis_cordova · Accepted solution]

Hi @Amafsha1 ,

Look what this guide indicates:

Interface Tracking

Interface tracking allows you to specify another interface on the router for the HSRP process to monitor in order to alter the HSRP priority for a given group.

If the specified interface's line protocol goes down, the HSRP priority of this router is reduced, allowing another HSRP router with higher priority can become active (if it has preemption enabled).

To configure HSRP interface tracking, use the standby [group] track interface [priority] command.

https://www.cisco.com/c/en/us/support/docs/ip/hot-standby-router-protocol-hsrp/9234-hsrpguidetoc.html#intracking

Regards

[Giuseppe Larosa · Accepted solution]

Hello Amafsha1,

if the tracked interface line protocol goes down, the interface is down for HSRP  and then the HSRP priority is lowered ( by 10 by default) on new HSRP hello messages. At this point  the other router, if configured fro pre-emption, can become the new HSRP active router for the group if its priority is higher then that of the current HSRP active router.

You just need  to give a difference of 5 for example priority 105 to the active router + standby <group> preempt on the standby router to achieve the desired  behaviour.

Multiple interfaces can be tracked on both routers if needed. Both routers need to enable preemption to provide also for restore of active HSRP when the interface line protocol is up again.

Hope to help

Giuseppe

[Amafsha1]

Thank you sir!  I have one more question, if you have time to answer it.  This is kind of relevant to what I'm attempting to accomplish.

[Jon Marshall]

Yes your interface would stay up although your BGP peering would go down. 

If this is a problem in terms of your HSRP tracking you need to look into using IP SLA as well. 

Jon

[Amafsha1]

Thank you Jon!