HSRP standby preempt

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Jan 18th, 2008
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I'm under the assumption that if you're using hsrp that 'standby preempt' would be mandatory if you actually want the gates to failover. Is this true? If not, under what circumstances would you not want to have preempt configured?


Thanks.


/rls

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Edison Ortiz Fri, 01/18/2008 - 09:02
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> you're using hsrp that 'standby preempt' would be mandatory if you actually want the gates to failover. Is this true?


Correct


__


Edison.

Danilo Dy Fri, 01/18/2008 - 09:06
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Hi,


IMHO, "standby preempt" enables the HSRP router with the highest priority to become active. For example, in the event that the router with higher priority is removed from the network, the router with lower priority (standby) will become active. When the router with higher priority is back, it will preempt a lower priority router (which is now the active) and send a coup message. When the lower priority router received the message, the router change to speak state and resigns (becomes standby)- and of course the higher priority router will become active.


If you don't configure a router with "standby preempt" that router will never become active.


Regards,

Dandy

Jon Marshall Fri, 01/18/2008 - 09:16
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Hi


The gates would failover even without standby preempt if the active router interface went down. As Dandy has pointed out when the router interface with the higher priority comes back on line if it does not have preempt configured it will not become the active gateway.


There is also the issue of interface tracking where you can decrement the priority if a tracked interface failed. Again in this scenario you would need preempt or the router with the higher priority would not take over.


HTH


Jon

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