From: Brian McGahan (brian@xxxxxxxxxxxxxxx)
Date: Fri Jul 12 2002 - 23:44:23 GMT-3
Johnathan,
Actually there's a little more to it than that. With IS-IS,
there are only two network types, point-to-point and broadcast. Unlike
OSPF however, there is no equivalent of the 'ip ospf network' command.
The IS-IS network type is dependent on the interface type.
Physical and multipoint NBMA interfaces are multipoint. The
only big difference between them is that split-horizon is disabled on
frame-relay physical interfaces. Point-to-point interfaces are (you
guessed it) point-to-point. Like OSPF, the IS-IS network type must
match for neighbors to become adjacent. Therefore, for two IS-IS
routers to become adjacent over NBMA, you need to have a combination of
physical and multipoint, or two point to point interfaces. This leads
us to two more issues that are worth mentioning.
1. IS-IS will not run over a hub and spoke NBMA
2. IP is not the transport protocol for IS-IS
In regards to the first issue, this means that you must have two
IP subnets if you are running a hub and spoke setup. Therefore you must
have two separate subinterfaces on the hub, or do a workaround such as a
GRE tunnel.
Regarding the second issue, this means that physical and
multipoint interfaces must have layer 2 to CLNS mappings. For
frame-relay this translates to:
frame-relay map clns [VC] broadcast
This article should help to clarify some more.
http://www.cisco.com/warp/public/97/isis-frint.html
HTH,
Brian McGahan, CCIE #8593
Director of Design and Implementation
brian@cyscoexpert.com
CyscoExpert Corporation
Internetwork Consulting & Training
http://www.cyscoexpert.com
Voice: 847.674.3392
Fax: 847.674.2625
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Jonathan V Hays
Sent: Friday, July 12, 2002 5:11 PM
To: ccielab@groupstudy.com
Subject: RE: ISIS - subinterface needed?
Thanks everyone for all the informative replies!
Jonathan
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Jonathan V Hays
Sent: Friday, July 12, 2002 2:17 PM
To: ccielab@groupstudy.com
Subject: ISIS - subinterface needed?
Group,
I just had an interesting experience configuring ISIS on two routers.
One router (R1) had two serial subinterfaces, one of which was
point-to-point to another router running ISIS (R2). Now R2 was not
configured with subinterfaces, just "interface serial 0" since it was
only connected to R1 (via frame relay). I could not get ISIS routes to
appear in the routing tables of either router.
After I changed R2 to a point-to-point subinterface the ISIS routes
popped into both routing tables.
The question is, why is the point-to-point subinterface necessary on
both ends for ISIS to propagate routes?
Jonathan
This archive was generated by hypermail 2.1.4 : Sat Sep 07 2002 - 19:36:28 GMT-3