Subject: Doubt on sending hello packets on NBMA networks

From: Srinivasa J Ragavan <[email-masked]>
Date: Mon, 9 May 2005 06:07:19 -0400

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)

Am i missing something here??

thanks
Srini

---

From: Acee Lindem <[email-masked]>
Date: Mon, 9 May 2005 09:10:25 -0400

>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