HSRP question

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Dec 30th, 2006
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Hi All,


While I was consolidating some HSRP information i found this paragraph:


"Only the standby (second highest priority) router monitors the hello messages from the active router. By default, hellos are sent every 3 seconds. If hellos are missed for the duration of the holdtime timer (default 10 seconds, or 3 times the hello timer), the active router is presumed down. The standby router is then clear to assume the active role. If other routers are sitting in the Listen state, the next-highest priority router is allowed to become the new standby router."


According to this paragraph, if only standby router monitors active hello, how will a new router joing the network with a higher priority and preempt enabled in the same HSRP group take over the active role ?


Thanks in advance,

Mohammed.

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ankbhasi Sat, 12/30/2006 - 07:53
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Hi Mohammed,


That is the main purpose of PREEMPT keyword.


When a new or old higher priority router comes up with preempt keyword configured it 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 and finally becomes a standby router and new router will take the role of active router.


HTH


Ankur


*Pls rate helpfull post


mohammedmahmoud Sat, 12/30/2006 - 09:48
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Hi Ankur,


Thanks alot for your perfect reply, lets recap the issue and correct me if i am wrong; normally only the standby router monitors the Hello messages from the active router, but in case of a new router joining in with a higher priority for this HSRP group and it is configured with preempt --> This new router sends a Coup message to the active router, forcing the active router to send a Resign message --> The new router becomes the new active router.


One last question; as for the formerly active router, would it go the standby state (instead of the formerly standby router, as it for sure has a higher priority)or to the listening state like any other low priority router in the HSRP group ?


Really thank you on your prompt, perfect answers.


best regards,

Mohammed Mahmoud.

mohammedmahmoud Sat, 12/30/2006 - 11:22
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Hi Ankur,


I have new findings which i wish you to comment on plus the prior post:


"Normally non Active or Standby routers are in the Listen state, If the Standby router fails or becomes the Active router; they go to the Speak state in order to go for an election as a Standby router as the current Standby router will either fail or go to the Active state"


Is this parapraph correct ?


"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."


Why Speak state not Listen state ?


Best regards,

Mohammed Mahmoud.

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