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Bronze

hsrp, standby preempt

HI every body!

i just want to confirm my test.

My cisco book says the command " standby preempt" causes the router to become active if its priority is higher than the current active hsrp router.

I was wondering if the command "standby 1 preempt" only makes the router active if its priority is higher than current hsrp router only or it also causes a router to become active if its priority is same as current active hsrp, but its ip address is higher than current active hsrp.

r1-----------sw-------------r2

r1:

int eo

ip address 199.199.199.1/24

no shutdown

standby 1 preempt

standby 1 preempt

standby 1 ip 199.199.199.10

r2:

int e0

ip address 199.199.199.2/24

no shutdown

standby 1 preempt

standby 1 ip 199.199.199.10

------------------------------------

Now i turned off both routers, then turned on r1 to ensure it becomes active hrsrp.

After i make sure r1 is active by " show standby", i turned on r2

i found that r2 becomes active and r1 becomes standby.

It appearas to me the command" standby preempt" not just make the router active hsrp if its current priority is higher than current active hsrp. If priorities are same, but the router has higher ip address than current active hsrp,the command "standby preempt" also make the router active hsrp.

Could any body confirm that this behavior is same across other platforms please?

I run the test on 2500 routers which are pretty old.

thanks a lot!

1 ACCEPTED SOLUTION

Accepted Solutions
Silver

Re: hsrp, standby preempt

HSRP active router selection is first determined by the configured priority value if same then by IP address. Since R2 has higher priority it becomes active router.

So its not Preempt command which changing but the HSRP active router selection protocol.

For more info read

http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094a91.shtml

The standby preempt command enables the Hot Standby Router Protocol (HSRP) router with the highest priority to immediately become the active router. Priority is determined first by the configured priority value, 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, the router sends a Coup message. When a lower priority active router receives a Coup message or a Hello message from an active, higher priority router, the router changes to the Speak state and sends a resign message.

1 REPLY
Silver

Re: hsrp, standby preempt

HSRP active router selection is first determined by the configured priority value if same then by IP address. Since R2 has higher priority it becomes active router.

So its not Preempt command which changing but the HSRP active router selection protocol.

For more info read

http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094a91.shtml

The standby preempt command enables the Hot Standby Router Protocol (HSRP) router with the highest priority to immediately become the active router. Priority is determined first by the configured priority value, 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, the router sends a Coup message. When a lower priority active router receives a Coup message or a Hello message from an active, higher priority router, the router changes to the Speak state and sends a resign message.

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