Re: Doubt on sending hello packets on NBMA networks

[Acee Lindem <acee at CISCO.COM>]

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
>
>