Re: Doubt on sending hello packets on NBMA networks

["Srinivasaragavan Jayaraman - CTD, Chennai" <srinivasarj at HCLTECH.COM>]

hi Acee,

	yeah i got it. but just for the sake of curiosity. can you give me
some more scenarious where this can happen?

Thanks
Srini

-----Original Message-----
From: Acee Lindem [mailto:acee at CISCO.COM]
Sent: Monday, May 09, 2005 6:40 PM
To: OSPF at PEACH.EASE.LSOFT.COM
Subject: Re: Doubt on sending hello packets on NBMA networks


Srinivasa J Ragavan wrote:

>hi All,
>
>I am a newbie to OSPF.
>can anyone help me out.
>this is with reference to the rfc 2328 sec. 9.5.1 whcih says
>"  If the router is eligible to become Designated Router, it
>            must periodically send Hello Packets to all neighbors that
>            are also eligible."
>
>but immediately in the next paragraph it says
>
>" It must also send an Hello Packet in reply to an
>            Hello Packet received from any eligible neighbor (other than
>            the current Designated Router and Backup Designated Router)"
>
>how can a non eligible router get a hello from a eligibe router if the
>eligible router is not going to send(tatz what the first argument says)
>  
>
Srini,
In the NBMA case (which is described in section 9.5.1), a non-eligible 
router
needs to reply to any eligible neighbor since it may not know the current
DR/BDR. There are a number of scenarios where this can happen including
the case where the non-eligible neighbor first comes up and receives a 
hello poll
from the current DR/DBR. The non-eligible neighbor needs to establish
bi-directional connectivity with the potential DR/BDR in order for its
local DR/BDR election to work.

Hope this helps,
Acee


>Am i missing something here??
>
>thanks
>Srini
>
>  
>
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