Hi, Gurpreet:

    It seems to me that router X is an ABR which connects to both backbone
area and area 1. If so, for router X, the route to router A is an intra-area
route because router X derives this route from a router lsa instead of a
type-3 lsa. In fact, this can be used as a criteria of determining
intra-area and inter-area routes.
    If router X derives a route based on a type-3 lsa it gets from router B,
then this route is an inter-area route for Router X and it will generate a
type-3 lsa and send it to Router A. But the type-3 lsa wouldn't be sent back
to the backbone area.
     Hopefully this will help.

Feng Xie

-----Original Message-----
From: Singh, Gurpreet [mailto:Gurpreet.SinghSPIRENTCOM.COM]
Sent: Tuesday, September 25, 2001 3:34 PM
To: OSPFDISCUSS.MICROSOFT.COM
Subject: Intra Area Routes

Hi

  According to RFC 2328 Setion 12.4.3
"only intra-area routes are advertised into the backbone, while both
intra-area and inter-area routes are advertised into the other areas."

This means that intra-area routes are advertised into backbone as well as
non-backbone areas and inter-area routes are not advertised to backbone
areas.

If a router X is connected to a router A (AS Boundary Router) in Area1 and
also router X is connected to Router B in the backbone area.

Then the route to Router A will be considered as inter-area or inter-area
with respect to router X ? i.e. Should the router X advertise the route to
Router A in a Summary LSA to Router B ?

Also if the router X should advertise the RouterA to Router B then what will
be considered as a inter-area route such that router X will not advertise it
to router B.

Gurpreet

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