Issue with HSRP Preemption

[Sharanjeet_Kumar]

Hi,

I am using HSRP in my lab with a default priority. But, having issue whenever my active router goes down, and later when it comes up then it is continuing with standby status not the active. I enabled Preemption that is also not working.

when my new active router goes down then the first active become active.

R1-> active --> goes down --> comes up --> becomes standby not active

R2-> standby-->becomes active

It is working fine with VRRP but not with HSRP.

Any help is appreciated

[Richard Burts]

Joseph

Yes, extremely unlikely. It is my understanding that in the scenario you describe both routers returning on line would send coup messages, the existing active peer would send a resign message, and essentially the result would be a new election.

I agree with your discussion about needing to set only one router priority in a router pair. But my comment was about why the original poster seems insistent that all routers have the default priority.

[Joseph W. Doherty]

Rick, exactly!  Interface IPs are a tie breaker for equal priorities when an active gateway is being elected.

Again, only OP can answer your question.  Mine was just a hypothetical reason that someone, not fully understanding HSRP, might want to only use default priority with preempt.  As OP found you can do that but preempt doesn't work as OP expected.  If someone did want to make a minimal, correctly working, HSRP config, I further described how that might be done.

[M02@rt37 · Accepted solution]

Hello @Sharanjeet_Kumar,

could you please share your HSRP config ?

Preemption is a feature in HSRP that allows a higher priority router to take over the active role if it becomes available again after a failure. Based on your description, it appears that preemption is not working as expected.

Waiting for your outputs, there are a few factors to consider:

--Verify the priority settings on both routers (R1 and R2). The router with the higher priority will become the active router. Ensure that R2 has a higher priority than R1 when both routers are up and running.

--Double-check that preemption is enabled on both routers. It should be enabled for the router that you want to regain its active status when it comes back up. You can enable preemption using the following command on the active router:

standby [group-number] preempt

--In HSRP, there is an option to track interfaces. If the tracked interface goes down, the router's priority is decreased, and if it comes back up, the priority is increased. If tracking is configured, it can impact preemption. Ensure that tracking is set up correctly and isn't causing any conflicts.

--Check the HSRP version on both routers (version 1 or version 2). Make sure that both routers are using the same version to avoid any compatibility issues.

Thanks.

[DanielP211]

Please paste the configuration. You have to have a higher priority on the active router.

[MHM Cisco World]

IOU1 is active and IOU2 is standby (SAME priority) 
the IP interface for IOU1 is higher than IOU2 (200 to 100)
when the IP interface tie break work ?

when BOTH router power ON in same time,
I config WR config and then power off/on BOTH routers and IOU1 elect as active 

Here I only reload IOU1 (old active) with preepmt option enable and there is no change in standby status even if IOU1 IP interface is higher.
so the Preempt as I mention in first comment is depend on priority only, and can not work with default same priority 

using track ?
there are two failure here 
one all router failed 
other is Uplink failed 
for Uplink failed track we use 
for all router failure you need to be sure that priority (with  what track add) of active is MORE than what we config in standby to make preempt option work 

[Joseph W. Doherty]

BTW, to recap, your problem isn't related to using the default priority but to using the same priority (across routers).

For preempt to work correctly, you need for a router you want to preempt all others to have the highest priority.  Such a router could have a default priority but other routers would need an explicit lower priority.  Or, other routers could have default priority but best router would need an explicit higher priority.

Lastly, in @MHM Cisco World's recent posting, it's noted IP tie braking works when routers are powered on at same time.  In practice, that's likely to be seen, but technically, it's when there's need to establish the active gateway.  In a concurrent power on, it's possible one router may come on-line faster and become the active gateway, so there too if you want to insure preemption, you need different priorities.  (As a recommendation, I would consider relying on interface IP poor practice.)

[MHM Cisco World]

@Joseph W. Doherty  both router can not power in same time or one power then other, that totally correct.
for lab I test like this
in real if you want to make both routers run HSRP in same time there is delay, but that other story LOL...
have a nice summer for you and your family 
MHM