HSRP preemption behavior

[darwinsanchez6774]

Good day, 

I have 2 routers R1 and R2. They are both configured with HSRP under standby group 1.

-R1 and R2 has the same priority of 100 

-R1 is the active router since it has z higher IP adddess of 10.1.1.3/24. While R2 is the standby with an IP of 10.1.1.2

-preemption is disabled for both routers

I shutdown the interface fa0/0 of R1 connected to the LAN to know if R2 will take over. And sufely it did. So I up the R1's interface fa0/0. I was expecting that R2 will stay the active router since preemption is disabled. However, R1 suddenly became the active router and that put R2 in standby. How come this happened?

Thanks in advanced xoxo😊

[Reza Sharifi]

Hi,

If preeamtion is not enabled, r2 should stay active.  Can you post relavent configs from both routers?

Also, can you post the output of sh stand 1" from both routers?

HTH

[rasmus.elmholt]

Hi
R2 should keep the state of active. Could you share the output from show stand brief?

What software versions and switch model are you using?

[Predrag Jovic]

Since there is no prieemtion configured, split brain scenario would be explanation for change of active router.
- at some point HSRP hello packets from R1 were not able to reach R2 router
- both devices become active routers (split brain)
- hello packets between from R1 started to be received on R2 and election process started
- R1 won election - equal priority, higher IP address wins
- R2 becomes standby router

Check logs (show logg) on R1 and R2 to confirm the above scenario (if loggs are still present and proper level of logging is/was configured on device).

[Julio E. Moisa]

Hi

I think other members have mentioned how it should works, R2 should be the active device. Now, in normal situation are you really sure they are working as active/standby?. I have seen situations where both routers are as active, because they have the same priority or there is no communication between both routers to exchange the HSRP packets. 

:-)