Hi, Vikas:

    My understanding is that two entries are added for a point-to-point link
if the adjancency is full. The first entry which is a first type link gives
the nbr rid and local IP address information. The second entry which is a
third type link gives the nbr ip address information. In fact, for the
second entry, some vendors use the network address and the mask. A short
comparison is given in RFC2328, p181, item 15 for thest two options.

Feng Xie

-----Original Message-----
From: Vikas B. Wadhwani [mailto:wvikasYAHOO.COM]
Sent: Monday, July 02, 2001 3:24 PM
To: OSPFDISCUSS.MICROSOFT.COM
Subject: Link State Advertisments

Hello all,
This is from RFC 1583

Else, if the state of the interface is Point-to-Point,
then add links according to the following:

If the neighboring router is fully adjacent, add a
Type 1 link (point-to-point) if this is an interface
to a point-to-point network, or add a Type 4 link
(virtual link) if this is a virtual link. The Link
ID should be set to the Router ID of the neighboring
router. For virtual links and numbered point-to-
point networks, the Link Data should specify the IP
interface address. For unnumbered point-to-point
networks, the Link Data field should specify the
interface's MIB-II [RFC 1213] ifIndex value.

If this is a numbered point-to-point network (i.e,
not a virtual link and not an unnumbered point-to-
point network) and the neighboring router's IP
address is known, add a Type 3 link (stub network)
whose Link ID is the neighbor's IP address, whose
Link Data is the mask 0xffffffff indicating a host
route, and whose cost is the interface's configured
output cost.

My question is, in case of a numbered point to point
network, are there 2 links added for a neighbouring
router? If a router is connected by a PPP link to
another, does the above mean that a Type 1 link and a
Type 3 link will be added to the router's LSA for a
neighbour?

Thanks,
-Vikas

=====

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