From: Ron.Fuller@xxxxxx
Date: Mon Aug 13 2001 - 14:10:11 GMT-3
For what its worth, IS-IS over IP is pretty dead as far as I can tell. TTL
is irrelevant due to this being a direct L2 encapsulation. Normal bridge
loop protection applies.
Really? From what I have heard from some ISPs as well as many of the
seminars at Networkers and other events, IS-IS is picking up steam as a
preferred IGP as it can carry IPv6 addresing and may be more desireable
that OSPF. Can anyone on the list validate/refute either side?
Ron Fuller, CCIE #5851, CCDP, CCNP-ATM, CSS Level 1, CCNP-Voice, MCNE
3X Corporation
rfuller@3x.com
"Peter Van Oene" <pvo@usermail.com>
Sent by: nobody@groupstudy.com
08/13/01 12:38 PM
Please respond to "Peter Van Oene"
To: ccielab@groupstudy.com
cc:
Subject: RE: isis on physical / multipoint interfaces
The layer two addresses reserved for ISIS are described in ISO 10589/RFC
1142. There are multiple addresses reserved for various sets of
routers. Yves references the AllL2's address.
For what its worth, IS-IS over IP is pretty dead as far as I can tell. TTL
is irrelevant due to this being a direct L2 encapsulation. Normal bridge
loop protection applies.
pete
*********** REPLY SEPARATOR ***********
On 8/13/2001 at 8:17 AM Chuck Larrieu wrote:
>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
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