Subject: [Isis-wg] rfc 1195 (another one!)

From: "Swati Rastogi" <[email-masked]>
Date: Tue, 28 Aug 2001 10:14:39 +0530

Hi,
The way as i understood IS-IS routing goes something like this .. i am a L1
router and i recieve a packet destined to some other area so i forward that
packet to my nearest L2 router. How i know that this packet does not belong
to my area is by looking at its address. Then once it reaches the L2 router
since it is aware of all the areas which it can reach it will forward the
packet in question to the appropriate router. It will extract the area
address also once again from the destination address in the packet.
I hope i am okay till now ..
Since everything is mentioned in the address itself and we can do all our
routing just by looking at the address then we is it said that "L2 routers
should include in their L2 LSPs a complete list of [IP address, subnet mask,
metric] specifying all IP addresses reachable in their area" [RFC 1195..
Section 1.3]. Even in dual IS-IS we specify the area so why isn't the entire
routing done just by looking at area prefixes.

Please comment.

Regards,
Swati

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From: Tayfun Gol <[email-masked]>
Date: Tue, 28 Aug 2001 11:05:35 -0400

> I hope i am okay till now ..

As far as OSI forwarding goes, you are.

> routing just by looking at the address then we is it said that "L2 routers

This again is valid for OSI forwarding only, you can not associate an
IP destination address to an area address prefix ( which is derived from
NSAP address, you would have an NSAP destination address for
forwarding OSI traffic, not IP )

Tayfun Gol