From: Peter van Oene (pvo@usermail.com)
Date: Mon Nov 04 2002 - 16:00:08 GMT-3
At 08:45 AM 11/4/2002 -0800, Ron wrote:
>Hi Banlan,
>
>In an IS-IS NBMA environment, all routers must be connected in a
>point-to-point method. Unfortunately, IS-IS doesn't have much flexibilites
>when it comes to defining the state of the interface ("ip ospf network"
>command).
>
>There are 2 types of hellos in an IS-IS network, LAN Hellos and
>point-to-point hellos. If your hub's FR configuration is in multipoint or
>the physical interface (defaults to multipoint), then it will be sending
>L1 and L2 IS-IS LAN Hellos to the spokes which in return sends
>point-to-point IS-IS Hellos back to the hub. Adjacencies will not be formed.
>
>The only way is to convert the hub to a point-to-point network and all
>will be well.
Just wanted to add that it is possible to run a partial mesh hub and spoke
topology in broadcast mode so long as your hub router becomes the
DIS. Because the spokes will not communicate directly as the hub will not
relay the ISO/ES-IS frames, spoke to spoke adjacencies will not form as
they normally would in a broadcast topology. However, the hub will use the
CSNP/PSNP mechanism to relay any relevant spoke LSPs to other spokes and
databases should remain in sync.
I do agree and recommend that point to point circuits are definitely the
easiest way to deal with L2 topologies of this nature, however the lab
rarely asks you for the best method :-)
Pete
>HTH.
>
>Ron.
>
> >From Banlan Chen <banlan.chen@lycos.com> on 4 Nov 2002:
>
> > Hi Group,
> >
> > A quick question about isis over NBMA. On the hub and spoke environment,
> > is it must to configure hub router as DR like OSPF?
> >
> > Thanks in advance.
> > Banlan
> >
> >
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