From: Robert Laidlaw (laidlaw@consecro.com)
Date: Tue Jul 15 2003 - 16:04:12 GMT-3
Being that IS-IS is a CLNS protocol, the Attached bit only provides a
default-route for CLNP. Per "Routing Tcp/IP vol.1 page 402,
"The problem is that the ATT bit is a CLNS function, and the IP process
cannot directly interpret the bit. There are two solutions to the
problem. The first solution is to enable IS-IS for CLNS on the
interfaces in addition to IS-IS for IP. This first solution works in a dual
CLNP/IP environment, but if IS-IS is being used as an IP-only routing
protocol, enabling CLNS routing just for default IP routes may be
undesirable. A second solution to the default route problem is
to configure a static default route on the L1/L2 router and configure
IS-IS to advertise the default with the command default-information
originate."
----- Original Message -----
From: "Leroy Harvey" <leroy.harvey@sbcglobal.net>
To: <polarccie@yahoo.co.uk>; <ccielab@groupstudy.com>
Sent: Tuesday, July 15, 2003 1:55 PM
Subject: RE: isis default
> Ok, I am new to this forum and not an ISIS expert. That being said, here
is
> my experience with ISIS.....from memory. Try each of the 2 methods I show
> below and let me know your results. )
>
> The concept of default information origionate only propigates to L2
routers,
> with no other commands to help it propigate to L1. L1 has no concept of a
> "default gateway" in the same manor that other protocols do. What you need
> to tell a L1 box is that it's L2 routers (same area) are "attached" (or
have
> knowledge) to routing information outside of their area. Default
information
> origionate only benefits L2 routers.
>
> In order to set the "attached" bit on L2 routers so that L1 routers see it
> and therefor set the default GW according to the L2 "attached" routers
that
> they see, you have to satisfy 2 requirements:
>
> First requirement
> The L2 router(s) in the subject area have to border at least one L2 router
> from another area.
> Second requirement can be satisfied by one of two methods
> You can use "clns router isis" instead of "ip router isis" (or use both if
> you like at one time)
> or
> You can use "ip router isis" with (I think) default information origionate
> on the L2 in that area
>
> Leroy
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> polarccie@yahoo.co.uk
> Sent: Monday, July 14, 2003 1:37 PM
> To: ccielab@groupstudy.com
> Subject: isis default
>
>
> Hi group...
> in a topology like
>
> r2s0
> r1------ -------r3
>
> this is the isis over nbma...
> r123 are in the same isis area.
> r1-r2 has a l1/l2 neighborship and
> r2-r3 has a l1 neighborship...
>
> when i, default-information-originate on r2...
> i can not get r3 receive the default...although r1 receives it.
>
> i checked the archieves
> tried clns routing on neighboring interfaces,
> another isis neighbor for r2 in a different area.still nothing.
>
> thank you.
>
>
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