From: Chuck Larrieu (chuck@xxxxxxxxxxxxx)
Date: Mon Aug 13 2001 - 12:17:38 GMT-3
thanks for your post. I found it interesting and a good starting point for
further research. did you use either of the following resources?
the information provided by Rad-Com and their alias protocols.com?
http://www.protocols.com/pbook/iso.htm
the RFC that deals with IS-IS over IP?
ftp://ftp.isi.edu/in-notes/rfc1069.txt
I won't say I've read, let alone understood, every word. I was unable to
find any indication of a MAC address field in any of the packet formats I
looked at. I was curious as to where this information come from? Is that a
Cisco implementation?
Also, I believe that in general frame relay by default doesn't replicate
anyone's packets. however, other protocols offer the means to make
adjustments based on need. IS-IS has no such tweaks.
yes, tunnel interface work. tunnels are point-to-point links. ( unless you
are one of those rare few who have been able to get a point-to-multipoint
tunnel to actually work :-> )IS-IS works fine and dandy over PTP's
thanks again. appreciate the sharing.
Chuck
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Yves Fauser
Sent: Monday, August 13, 2001 5:57 AM
To: Cox, Bryan; 'ccielab@groupstudy.com'
Subject: Re: isis on physical / multipoint interfaces
Hi all,
jonatale@earthlink.net asked me if an isis clns paket does have a TTL field,
so I
read some a bit more and came to this conclusion :
Isis doesn't use clns at all, isis used it's own packet format (isis PDU,
unlike
ospf that uses an IP packet). clns has a lifetime field, which is the same
as a
TTL. The isis PDU doesn't have a lifetime field. Isis PDU's also don't have
a
Layer 3 multicast destination address, they only have a MAC multicast
address of
0180.C200.0015. From my understanding a FR HUB router with a physical or
multipoint interface will never "replicate" a isis PDU from Spoke to Spoke.
Also
it is the general rule for a hello packet to find neighbors. A spoke will
never be
a neighbor of another spoke regardless what you do.
jonatale@earthlink.net also came up with the idea of creating a tunnel
between the
two spokes, this works fine.
Yves
Yves Fauser wrote:
> Bryan,
>
> I think you are right, we may both have some kind of a IOS Version
trouble,
> but more likely it will not work on Point-to-Multipoint or Physical FR
> interfaces in any Version. I saw a scenario that worked with isis on FR
PtM
> interfaces (in ECP1), but this scenario had a major difference, one spoke
was
> a level-1 and the other spoke was a level-2 router of another Area. I just
> tried it out again, and it works in my home lab. After reading some more
of
> Doyle VolI I think I know why (please correct me if I'm wrong guys).
>
> Doyle, Page 607 :
> "Unlike OSPF ISIS router attached to a broadcast multi-access network
> establishes adjacencies with all of its neighbors on the network, not just
the
> DR. Each Router multicasts its LSP's to all of his neighbors, and the DR
uses
> a system of PDU's called Sequence number PDU's (SNP) to ensure that
flooding
> is reliable."
>
> Doyle, Page 608 :
> "As the L1 and L2 priorities suggest, separate DR's are elected on a
network
> for level 1 and level 2."
>
> In OSPF the DR is like a "route reflector" in BGP. In ISIS the DR is only
used
> to control the Exchange of LSP's between the neighbors. Since the ISIS and
> OSPF multicast/unicast will have a TTL of 1, they will die on the FR HUB.
In
> OSPF, when the DR is the HUB, there is no need for the LSA to take 2 hops
> (Reflection). In ISIS it has to take 2 hops to work, and this is not
possible
> since the TTL is 1. If you have 2 Spokes, one is a level-1 and the other
is a
> level-2 it works, since two separate adjacencies are build. If both are
> level-1 or both are level-2, it will not work since the DR concept of ISIS
has
> no knowledge of NBMA Networks. If you have 3 spokes you can't use this
trick
> anymore since you must have either 2 level-1 1 level-2 routers ore the
> opposite.
>
> Any comments are more than welcome,
>
> Good luck, Yves
>
> "Cox, Bryan" wrote:
>
> > Group,
> >
> > I have come to the conclusion that ISIS won't run in a frame-relay
> > environment with physical or multipoint interfaces without a full-mesh.
> > Even with "frame map clns <dlci> broadcast" on the spokes and hub I
never
> > see the ISIS hellos being received at a spoke from another spoke. Thus
no
> > adjacency is formed between the spokes.
> >
> > In a full mesh I see the appropriate hellos between all points in the
> > frame-relay network. IS-IS forms adjacencies and all routes are
installed
> > in the table.
> >
> > Does anybody have any working configs for a hub and spoke environment
with
> > point-to-multipoint or physical interfaces that they can post that say
> > otherswise? Or am I on the right track?
> >
> > Thanks,
> >
> > Bryan
> > San Jose October 25th
> > **Please read:http://www.groupstudy.com/list/posting.html
> **Please read:http://www.groupstudy.com/list/posting.html
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