Subject: Re: Identification of neighbors in PTP links

From: "Naidu, Venkata" <[email-masked]>
Date: Fri, 31 May 2002 09:33:46 -0400

Balaji, Acee,

-> (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.)
->
-> 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.

  In Option 1, P2P stub link represents neighbor IP address
  and not local interface IP address.

  More over, the neighbor IP address is used as the next
  hop for all the SPF routes through the neighbor router.
  Though, next hop IP address is not required for P2P links
  (numbered or unnumbered) - because the L3->L2 address
  resolution won't arise when forwarding packets in case of
  P2P links, most of the implementations still uses neighbor
  IP address as the next hop for all those routes.

  For all the above reason, the neighbor IP address change
  might results in re-originating and/or re-computing SPF.

--
Venkata.

---

From: Acee Lindem <[email-masked]>
Date: Fri, 31 May 2002 09:43:29 -0400

>   and not local interface IP address.

I guess I didn't even support this option this time around
since option 2 results in fewer routes in the OSPF routing
domain.

>   might results in re-originating and/or re-computing SPF.

The router whose IP address changes should be responsible for
re-originating their LSA. This will result in SPF computations on
other routers in the OSPF area. If you perform an SPF when the
IP source address changes you'll end doing another one when you
receive the changed LSA.

--
Acee