Re: [OSPF] OSPF GR query

Acee Lindem <acee@cisco.com> Thu, 05 October 2006 15:11 UTC

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Date: Thu, 05 Oct 2006 11:10:33 -0400
From: Acee Lindem <acee@cisco.com>
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To: Khan Amir-G20247 <amirkhan@motorola.com>
Subject: Re: [OSPF] OSPF GR query
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Khan Amir-G20247 wrote:
> Hi Ace 
>
> But reaching to a FULL state is not one of the conditions for Helper to
> quit Helper mode, I guess a Helper who has reached 
> to FULL state with its restarting router will wait for Grace LSAs to be
> flushed or GR timeout to happen for exiting Helper mode.
>   
No - The presumption is when you reach FULL state you don't need to "quit"
helping - you have "finished" helping. Over the years, there have been a
few situations that could have been better documented - however, this never
caused any confusion in the past.

Thanks,
Acee

> Regards
> Aamir
>
>
> -----Original Message-----
> From: Acee Lindem [mailto:acee@cisco.com] 
> Sent: Thursday, October 05, 2006 8:00 PM
> To: Khan Amir-G20247
> Cc: ospf@ietf.org
> Subject: Re: [OSPF] OSPF GR query
>
> Hello Amir,
>
> Khan Amir-G20247 wrote:
>   
>>  
>>
>> Hi
>>
>> I have query related to OSPF Graceful Restart. 
>>
>> Consider this scenario: 
>>
>>  
>>
>> - Three Routers R1, R2 and R3 connected via Broadcast networks. 
>>
>>  
>>
>>  
>>
>>  
>>
>> - Where R1 is a DR on both the segments, where as R2 and R3 are in 
>> DR-other
>> - Now R1 wants to perform GR, R2 and R3 agrees to be its Helpers. 
>> - Now after restart R1 will try to form adjacency with both R2 and R3.
>>     
>
>   
>> - Lets say R1 and R2 had become FULL, while R1 and R3 had reached
>> Exstart state.   Now at this time R2 receives an LSA (any type 1-5 and
>> 7, from some other router existing in the same area, not pictured 
>> here) which he needs to flood to R1.
>> - This will force R2 to quit Helper Status, while R1 and R3 are still 
>> in process of forming adjacency.
>>   
>>     
> Since he has reached FULL state, he is no longer a helper router.
>   
>> Considering above scenario, my doubts are: 
>>
>> - How will R1 come to know that its Helper R2 has quit? 
>>   
>>     
> Since he has reached FULL state, he is no longer a helper router.
>   
>> - Will the adjacency between R1 and R2 needs to go down, as R2 quits 
>> helper mode?
>>   
>>     
> No
>   
>> - Will this effect the adjacency formation of R1 and R3?
>>   
>>     
> No. R3 MAY exit helper status and re-originate a new router LSA if he
> receives the new LSA before reaching FULL state with R1 AND he is has
> strict-LSA-checking configured.
>
> Hope this helps,
> Acee
>   
>>  
>>
>> Regards
>> Aamir
>>
>>  
>>
>>
>>   
>> ----------------------------------------------------------------------
>> --
>>
>> _______________________________________________
>> OSPF mailing list
>> OSPF@ietf.org
>> https://www1.ietf.org/mailman/listinfo/ospf
>>   
>>     
>
>   

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