From: Peter van Oene (pvo@usermail.com)
Date: Tue Jul 15 2003 - 17:56:17 GMT-3
At 02:04 PM 7/15/2003 -0500, Robert Laidlaw wrote:
>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,
This is an old issue and not currently the case. IP only ISIS boxes dig on
the ATT bit just fine. Further, IS-IS is an ISO protocol that was designed
to route for CLNS, but is not itself a CLNS protocol (ie defined in the ISO
specs for CLNS)
> "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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