From: Chris Lewis \(chrlewis\) (chrlewis@cisco.com)
Date: Wed Aug 24 2005 - 08:29:32 GMT-3
Good comments Scott,
I'd also like to point out one more thing that may catch some people out regarding configuring a NET in a format like 3940.0100.0100.0600.00
The parser will take it, but the config will transpose as follows:
router isis
net 39.4001.0001.0006.0000
This is all fine, but if for example you try to enter a vlaue of A940.0100.0100.0600.00 you hit a snag
Router1(config-router)#net A940.0100.0100.0600.00
Translating "A940.0100.0100.0600.00"...domain server (255.255.255.255)
^
% Invalid input detected at '^' marker.
The reason for this is that the first byte will be assumed to be the AFI, which has a maximum vlaue of 99, as it is specified in binary coded decimal.
Chris
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Scott Morris
Sent: Tuesday, August 23, 2005 10:07 PM
To: 'Arun Arumuganainar'; 'Hictor Fernandez'; 'Stefan Grey'; ccielab@groupstudy.com
Subject: RE: ISIS address rule question. IEWB
A little off... (but close!)
Per specs:
AFI is 1 byte (2 hex characters) (but not actually required, which confuses a lot of people) Area/address is a 1-12 byte field (2-24 hex characters) that is generally determined by the rules of each AFI type.
47. and 49. are common AFI's as they're set aside as "private" but generally irrelevant in a lab network anyway!
The system-id is required to be 6 bytes (not just a Cisco thing)
The N-Selector as you said is required to be .00 for a router/pseudo-node in ISIS. In ATM, it can be anything you want it to be, but .00 is easier to remember once! :)
Scott
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Arun Arumuganainar
Sent: Tuesday, August 23, 2005 10:51 PM
To: Hictor Fernandez; Stefan Grey; ccielab@groupstudy.com
Subject: Re: ISIS address rule question. IEWB
> Your'e told that "as the IS-IS NET address must start and end to one
> octet
> "<-
I don't think this is a valid statement . !!!
1) Address can be of length 8 to 20 Bytes ( excluding N-Selector )
2) Length of System ID should be same . Cisco convention is 6 Bytes .
3) N-Selector is left to 00 for IS - systems i.e For Routers N-selector will be always set to 0
Note : If you follow NSAP format first Bytes should be AFI which 2 bytes .
When you are using private NSAP address AFI would be 49.
Cisco Routes understand non-NSAP formats ( that do not mandates single byte
AFI) also .
You can have 3940.0100.0100.0600.00
Here 3940 ==> Area ID
0100.0100.0600==> System ID
00==> Nselector for IS ( Routers )
Hope this helps .
Thanks and Regards
Arun
----- Original Message -----
From: "Hictor Fernandez" <gnakh@telefonica.net>
To: "Stefan Grey" <examplebrain@hotmail.com>; <ccielab@groupstudy.com>
Sent: Tuesday, August 23, 2005 9:27 PM
Subject: Re: ISIS address rule question. IEWB
> Hi again,
>
> It's confusing you... It's not telling you that you're forced to have
> the first byte equal to 00.
> Remember how an NET address is REPRESENTED for human reading:
> AA.aaaa.aaaa.aaaa.aaaa.aaaa.aaaa.ssss.ssss.ssss.NN (AA and NN are 2
> bytes that are not shown together, are the rest of groups of 16 bits)
> They're telling you they're going to place 3490 beginning in the
> second
byte
> instead of beginning the NSAP with 34, and that 00 is being used to
> fill
the
> AA byte.
> That is: instead of using 34.9000.0100.0100.0600.00, use
> 00.3490.0001.0001.0006.00, that's easier to read, it belongs to area
00.3940
> and has 0001.0001.0006 as system ID.
>
> Your'e told that "as the IS-IS NET address must start and end to one
> octet
> "<- this just refers as how it is represented... , but you've never
> been forced to use 00... in fact, any NSAP address must start and end
> with one octet... isn't it funny?
>
> I'm not English and trying to express myself it's quite hard, I hope
> this
is
> clear enough.
>
> Regards
>
> Hictor
>
> ----- Original Message -----
> From: "Stefan Grey" <examplebrain@hotmail.com>
> To: <gnakh@telefonica.net>; <ccielab@groupstudy.com>
> Sent: Tuesday, August 23, 2005 5:42 PM
> Subject: Re: ISIS address rule question. IEWB
>
>
> >
> > Look on the brakedown from the IEWB workbook (this appears some
> > times in
> the
> > workbook so it isn't just a mistake)
> >
> > Task: configure the net address as 13456
> >
> > brakedown,explanation:
> >
> > isis network entity title (NET address are in the ISO NSAP format,
> > and
are
> > denoted in hexadecimal format. The above requirement states that
> R1,R3,R4,R5
> > and R6 be configured in IS-IS area 13456. In hexadecimal, this
> > number converts to 3490. However, as the IS-IS NET address must
> > start and end
to
> > one octet, and additional 00 has been added to the beginning of the
> address.
> >
> > Could anybody comment???
> >
> > >From: Hictor Fernandez <gnakh@telefonica.net>
> > >Reply-To: Hictor Fernandez <gnakh@telefonica.net>
> > >To: "Stefan Grey" <examplebrain@hotmail.com>,
> > ><ccielab@groupstudy.com>
> > >Subject: Re: ISIS address rule question.
> > >Date: Tue, 23 Aug 2005 17:35:59 +0200
> > >
> > >Hi all,
> > >
> > >1st. time I've heard of that...
> > >Last octet (n-selector) is what makes that NSAP address the NET, 00.
> First
> > >byte, 34 or 49 here, part of the area address (up to 13 bytes).
> > >
> > >I hope this helps
> > >
> > >best regards
> > >Hictor
> > >
> > >REM: NSAP ADDRESS = AreaID (1..13 bytes), SysID (6 bytes), NSEL (1
byte),
> > >and for the NSAP address to be the NET, NSEL=0x00
> > >
> > >----- Original Message -----
> > >From: "Stefan Grey" <examplebrain@hotmail.com>
> > >To: <ccielab@groupstudy.com>
> > >Sent: Tuesday, August 23, 2005 4:27 PM
> > >Subject: ISIS address rule question.
> > >
> > >
> > > > There is a rule that the Net address should start and end with
> > > > the
> same
> > > > octet. While doing different labs I can't uderstand it.
> > > >
> > > > 1. 3490.0001.0001.0006.00
> > > > 2.490125.0001.0001.0006.00
> > > >
> > > > Why the first address is incorrect. And to correspond to the
> > > > rule
> above
> > >we
> > > > should use the address 00.3490.0001.0001.0006.00
> > > >
> > > > But the second is correct. I just can't understand it event
> > > > writing
> this
> > > > addresses in binary.
> > > >
> > > > Could anybody explain?? thanks;)
> > > >
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