State Change/Timers in hsrp2

[Stephan Lache]

Hi Guys,

I have configured a simple

hsrp

setup.

Two routers in one

hsrp

group. ( see picture)

The timers are

default ( hello: 3 holddown:10)

When i

ping 8.8.8.8

from the VPC i don´t see any packet loss when the active  role changes from Router 1 to Router 2.

( initiated by

shutdown of Gi0/1

on Router1)

The standby debug tells that the transition happens in milliseconds.

I don´t understand that behavior, when the default timers are in place.

Shouldn´t take the transition 10 seconds with the default timers?

Can someone explain this ?

Thanks

Stephan

hsrp setup

[MHM Cisco World]

Test these time by shuwdown the port in SW not port in router.

[Stephan Lache]

Thanks for the help. 

[MHM Cisco World]

You are so so welcome 

Have a nice summer 

MHM

[MHM Cisco World]

this color packet is resign which send by active or standby router when you shut down the HSRP interface. 
why I suggest shut the interface of SW? because the shut of SW interface is not make HSRP send this message and here the hold time of hello is work 
just more info. any one read this post later 
have a nice summer 
MHM

[David Ruess]

Hello,

The timers should dictate the failover, yes. I labbed this up and noticed a couple things. When I shut down the interfaces attached to the HSRP process once or twice there was no loss of pings and the packet captures didn't really reveal anything out of the ordinary. When I shut down the switch interface it took about 10-12 seconds to resume pings.

Best guess is when you shut down the interface attached to the process it signals the other side to

pre-empt

immediately. Like I said though I didn't see anything in packet captures or out of normal behavior. I would try it a couple times shutting down different interfaces. It being a lab environment you can only get so close to actual gear sometimes. 

-David

[Peter Paluch · Accepted solution]

Hello,

My friends, please allow me to join.

I agree with MHM and David.

David, you are particularly close to the correct answer. When shutting down an interface on a router that runs HSRP and is Active, right before the interface goes down, the router sends out the HSRP Resign message (there are three messages in HSRP: Hello; Coup to yank the Active role; Resign to step down from the Active role) to inform the standby group that the Standby router needs to take over immediately. This shortens the convergence to the new Active router considerably.

A router can send a Resign message anytime it knows it is no longer eligible to be Active. That can happen if the router's interface is shut down by a command, or when the router's HSRP priority falls below a certain threshold and the HSRP is configured to shut down completely instead of continuing to run.

Shutting down the port on a switch is an unexpected event to the router, and by the time it finds out the link is down, it's too late to send the Resign message since the port is already down. In that case, the convergence takes the usual 10 seconds or so.

Best regards,
Peter

[Stephan Lache]

Thanks Peter,

Now I understand the scenario!

Regards

Stephan

[Stephan Lache]

Thank you David.