From: Fred Ingham (fingham@cox.net)
Date: Thu Oct 02 2003 - 16:27:09 GMT-3
Ken: Not a dumb question but the answer is in the RFC (hint).
" The ID field may be from one to eight octets in length, but must have
a single known length in any particular routing domain. Each router
is configured to know what length is used in its domain. The SEL
field is always one octet in length. Each router is therefore able
to identify the ID and SEL fields as a known number of trailing
octets of the NSAP address. The area address can be identified as
the remainder of the address (after truncation of the ID and SEL
fields). It is therefore not necessary for the area address to have
any particular length -- the length of the area address could vary
between different area addresses in a given routing domain."
Cisco routers are configured for a 6 octet ID and a 1 octet SEL.
Fred
----- Original Message -----
From: <Ken.Farrington@barclayscapital.com>
To: <fingham@cox.net>; <ccielab@groupstudy.com>
Sent: Thursday, October 02, 2003 2:50 PM
Subject: RE: ISIS Network Entity Title
> so I can configure on my router as you have explained, the first two (3
just
> wipes me out)
>
> router isis
> net 47.0000.0000.0001.00
>
> or
>
> router isis
> net 47.0001.0000.0000.0001.00
>
> How does the router know that the router isis process is in area 47 or
> 47.0001.
>
> Sorry if this sounds really dumb.
>
> Thx, Ken
>
>
> -----Original Message-----
> From: Fred Ingham [mailto:fingham@cox.net]
> Sent: 02 October 2003 19:31
> To: Ken.Farrington@barclayscapital.com; ccielab@groupstudy.com
> Subject: Re: ISIS Network Entity Title
>
>
> Ken: The NET can be from 8 to 20 bytes. The SEL and ESI fields are
> always 1 and 6 bytes respectively for cisco routers. Anything in front of
> this is the area id. Refs are Dolye, Vol I, and RFC 1629.
>
> NET must begin with a single octet, the AFI (Authority and Format
> Identifier)
>
> Examples:
> 47.0000.0000.0001.00 is area id 47
> 47.0001.0000.0000.0001.00 is area id 47.0001
> 47.0004.004d.0001.0001.0c11.1111.00 is area id 47.0004.004d.0001
> which can also be read as AFI 47, domain 0004.004d, area 0001
>
> So, to answer your question the area id can be 1 or 3 (or more) bytes.
>
> HTH, Fred
>
> ----- Original Message -----
> From: <Ken.Farrington@barclayscapital.com>
> To: <ccielab@groupstudy.com>
> Sent: Thursday, October 02, 2003 12:29 PM
> Subject: ISIS Network Entity Title
>
>
> > Guys,
> >
> > v.quick one indeed.
> >
> > Lots of examples of NETs on the www. Can I just clarify a couple of
> points
> > (MAINLY THE LENGTH OF THE AREA ID is it 1 byte of 3?) :-
> >
> > I have confiured this
> >
> > router isis ken
> > net 47.1000.5000.0001.0000.00
> >
> > the first xx.xxxx of the net is an area ID - this is a static size and
> > always 3 bytes?
> > the next fields are the system ID (shortest being xxxx.xxxx (4 bytes),
> > longest being xxxx.xxxx.xxxx.xxxx.xxxx.xxxx.xxxx.xxxx (16 bytes)
> > the last two are NSAP xx (1 byte)
> >
> > Is this correct??????????????????????????????????
> >
> >
> >
> > Tested below
> > --------------------
> > R6(config-router)#no router isis ken
> > R6(config)#router isis
> > R6(config-router)#net 47.1111.0000.00
> > %IS-IS: Invalid NET length
> > R6(config-router)#net 47.1111.0000.0000.00
> > R6(config-router)#no router isis
> > R6(config)#router isis
> > R6(config-router)#net
> > 47.0000.1111.1111.1111.1111.1111.1111.1111.1111.1111.00
> >
^
> > % Invalid input detected at '^' marker.
> >
> > R6(config-router)#net 47.0000.1111.1111.1111.1111.1111.1111.1111.1111.00
> > R6(config-router)#
> >
> >
> >
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