From: Chris Lewis \(chrlewis\) (chrlewis@cisco.com)
Date: Tue Jun 28 2005 - 13:08:42 GMT-3
Ahh, I understand what you are getting at now.
As long as the system ID is 6 bytes, both ff.systemid.00 and
00.00ff.systemid.00 are valid, it just depends how long the overall
address has to be, depending on question requirements. The area ID has
to be between 1 and 13 bytes in length. However, be careful, the first
byte in the area ID can have special meaning, and is known as the AFI,
specifying a top-level ISO addressing authority. In a private network,
this should not matter though and the common practice is to set the AFI
to the value 49, which is private addressing for NSAPs.
Chris
-----Original Message-----
From: san [mailto:san.study@gmail.com]
Sent: Tuesday, June 28, 2005 10:02 AM
To: Chris Lewis (chrlewis); lab
Subject: Re: ISIS Networks
Chris,
Can you explain, why
ff.systemid.00 cannot be used at ISIS net while converting "255"
decimal to hex .
I would like to know the reason about prefix "00.00" for
"ff.systemid.00". whether its a compulsary prefix to be attached ?
/SAN
On 6/28/05, Chris Lewis (chrlewis) <chrlewis@cisco.com> wrote:
> San,
>
> I don't quite understand what you are saying.
>
> It is safe to assume that anything given to you in the formate
> 49.0255.x.x.x.00 is already in hex.
>
> It is also safe to assume that if you are told in the question, an
> area has to have a value, say 255, it must be converted in to hex
> before being used in the NET value.
>
> The only significance to the number of x's in my post was that each
> value between the periods will have 4 characters.
>
> The key issue is that the six bytes before the n-selctor are the
> system ID, anything before that is the system ID, so in the example
> you give the area ID will be 00.00ff.x assuming that in your case x
> represents the two byte value that is inserted between periods in the
> NET value format.
>
> Chris
>
> -----Original Message-----
> From: san [mailto:san.study@gmail.com]
> Sent: Monday, June 27, 2005 9:03 PM
> To: Chris Lewis (chrlewis)
> Cc: ccie2be; Lee Carter; CCIE LAB
> Subject: Re: ISIS Networks
>
> Chris,
>
> net 49.0255.x.x.x.x.00 if its given in hex & equivalent area id in
> decimal will be a huge number correct ?
>
> For the above question (255 in decimal to net value )
> ff.x.x.x.x.00 => is wrong value ? No assumptions of Zero at begining
> is it ??
>
> 00.00ff.x.x.x.x.00 => is the correct value !!
>
> /SAN
>
>
> On 6/27/05, Chris Lewis (chrlewis) <chrlewis@cisco.com> wrote:
> > One last point, consider the format of the NET.
> >
> > The NET can be 8-20 bytes, with the last byte set to zero. The 6
> > bytes
>
> > directly in front of this last byte are the system ID. All bytes in
> > front of the system ID are the area ID. So if you are given 255 in
> > decimal as the area ID, look at it like this:
> >
> > 00.00FF.xxxx.xxxx.xxxx.00
> > Area ID.System ID .N-selector and must be 0
> >
> > Chris
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of ccie2be
> > Sent: Monday, June 27, 2005 5:12 PM
> > To: 'Lee Carter'; 'CCIE LAB'
> > Subject: RE: ISIS Networks
> >
> > Lee,
> >
> > As long as you remember that the NET is in HEX, you should be fine.
> > In all likelihood, the task will be worded in such a way there won't
> > be any ambiguity.
> >
> > However, if you're unsure, ALWAYS ask the proctor.
> >
> > Tim
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of Lee Carter
> > Sent: Monday, June 27, 2005 5:50 PM
> > To: CCIE LAB
> > Subject: ISIS Networks
> >
> > All,
> >
> > Ok, so when defining isis net's I have seen two different solutions
> > where they say.. Put a particual isis network in say net 255 to keep
> > it easy.
> >
> > One solution would use:
> >
> > net 49.0255.xxxx.xxxx.xxxx.00
> >
> > The other (which I believe is correct) would use:
> >
> > FF.0000.xxxx.xxxx.xxxx.00
> >
> > Since the firt two bits are in HEX.
> >
> > Thoughts?
> >
> >
> >
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