HSRP (preempt and timer)

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Nov 17th, 2007
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Say there are two Router R1 and R2 configure with HSRP. R1 is active and R2 is standby. R1 has the command "standby 1 preempt" configure on it. Both R1 and R2 configure with "standby 1 timers 5 10.


1) Now there is a network failure on R1.

I know R2 will take over as active. How long will R2 take over as active from R1?

is it depend on holdtime which is 10 sec in this case?


2) If R1 has recover, will R1 regain as active router from R2 straignt away? Must R1 have to wait to regain its active status? I heard in real world, R2 would still be active until a reboot on R2 then R1 will regain his active status.

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glen.grant Sat, 11/17/2007 - 02:07
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If R1 fails then R2 should take over over . As soon as R1 comes back online and if R1 has a higher hsrp priority configured and also has the preempt command configured it will become the active side as soon as the router or interface becomes active again , that is what the preempt command is for .

bvsnarayana03 Sat, 11/17/2007 - 02:17
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Preempt enables the device with highest priority to take over as the active device (priority is configured manually else highest IP adress device is considered active).


1. If R1 is down, then R2 will take holdtime configured(10sec) to declare itself as active.


2. When R1 comes UP, again it sends HELLO indicating itself as highest priority device. Now here is the role of preempt, when R2 recv hello with R1 as highest priority then it resigns & gives the control back to R1. Again this transition happens in holdtime configured.

anand.dahiya Thu, 11/22/2007 - 00:31
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Hi

The HSRP preemption feature enables the router with highest priority to immediately become the Active router. Priority is determined first by the priority value that you configure, and then by the IP address. In each case a higher value is of greater priority.


When a higher priority router preempts a lower priority router, it sends a coup message. When a lower priority active router receives a coup message or hello message from a higher priority active router, it changes to the speak state and sends a resign message.


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