VRRP Failover

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Mar 25th, 2010
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Hi,

     I have been doing some proof of concept testing with VRRP & have a question re failover conditions.

What i found was that when the topology changed with a backup link between the routers & rapid per vlan spanning tree, then the standby router went Active for around 30 seconds. However with HSRP configured on the same routers, there is no change it the active standby relationship between HSRP.

If i change the advertisement timer to another value, i.e. 3 seconds, then that is the delay before the standby router goes active.

So if i change the advertisement timer to 3, then the standby router goes active after 3 seconds, then back to standby after 30 seconds.

Is this normal operation for VRRP?


Thanks

Colin

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Reza Sharifi Thu, 03/25/2010 - 18:24
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Colin,


Check your VRRP configuration.  VRRP and HSRP default timing intervals are pretty much the same. As far as priority and preemption, they are also pretty much identical.  Overall, there is not really much of a difference between there 2 protocols unless there is some thing else that may be misconfigured


HTH

Reza

Ganesh Hariharan Thu, 03/25/2010 - 22:26
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Hi,

     I have been doing some proof of concept testing with VRRP & have a question re failover conditions.

What i found was that when the topology changed with a backup link between the routers & rapid per vlan spanning tree, then the standby router went Active for around 30 seconds. However with HSRP configured on the same routers, there is no change it the active standby relationship between HSRP.

If i change the advertisement timer to another value, i.e. 3 seconds, then that is the delay before the standby router goes active.

So if i change the advertisement timer to 3, then the standby router goes active after 3 seconds, then back to standby after 30 seconds.

Is this normal operation for VRRP?


Thanks

Colin

Hi Colin,


It can be possiblity that as the timer and the funcationality of VRRP modes,HSRP uses  a default hello countdown timer for 3 seconds, along with a hold timer that spans for 10 seconds where as VRRP uses a faster timer of 1 second for its default hello, and a 3-second hold timer as well.


But in VRRP only master router sends hello packets. The backup routers only send packets when negotiating a new master. Unfortunately, this makes it more difficult to detect all routers that are part of a redundancy group within a subnet.So in your case if the link between the master and backup was down for more than 1 sec at that time backup router would have assumed the funcationalty of master once the link restored as preempt is default behavior in VRRP master once again gains the role for master.


Hope to Help !!


Remember to rate the helpful post


Ganesh.H

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