Subject: Identification of neighbors in PTP links

From: "Balaji R (Networking) - CTD, Chennai." <[email-masked]>
Date: Fri, 31 May 2002 15:16:19 +0530

Hello,

I have a question regarding the association of neighbor data structure with
a received hello packet.

Section 10.5 states that the neighbor is identified by the source IP address
on all types of networks except point-to-point links. In point-to-point
links, router ID found in the OSPF header must be used to locate the
neighbor.

My implementation maintains neighbors on a per-interface basis and knows the
interface through which the packet came in. My question is, is there any
issue in using the source IP address to locate the neighbor as is done in
other types of networks? Are there any implications in doing so? (Actually,
on numbered ptp links, we would have to check if the source IP address has
changed every time we receive a packet, since we originate router LSA with
the neighbor's IP address. I guess we would have to re-originate a new LSA
if the neighbor's IP address changed. So, I thought locating the neighbor
based on source IP address would hanlde this case more easily.)

I can understand that using router ID to identify the neighbor can present
problems with respect to multi-homing in multi-access networks. However, I
don't fully appreciate why router ID must be used in point-to-point links to
identify neighbors.

Thanks,
Balaji.R.

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From: Amit Srivastava <[email-masked]>
Date: Fri, 31 May 2002 04:10:42 -0700

Hi Balaji R
You can use ip source address to identify the neighbour stucture for numbered point-to-point link but for un-numbered u will have to use
Router id only so to make consistence it is better to use router id as the unique key.
regards
Amit
  "Balaji R (Networking) - CTD, Chennai." <[email-masked]> wrote: Hello,

Thanks,
Balaji.R.

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From: Acee Lindem <[email-masked]>
Date: Fri, 31 May 2002 09:10:32 -0400

> based on source IP address would hanlde this case more easily.)

For P2P links, the link data in your router link contains your interface IP
address - not your neighbors. You should not have to originate a new router
LSA if your neighbor's IP address changes.

--
Acee