From: Lee Donald (Lee.Donald@t-systems.co.uk)
Date: Tue Mar 29 2005 - 13:05:40 GMT-3
Dillon,
I have already drawn out the zero's and ones but I can't see /23 ?
How does /23 work ?
-----Original Message-----
From: Dillon Yang [mailto:gzdillon@hotmail.com]
Sent: 29 March 2005 16:58
To: Lee Donald
Cc: Group Study
Subject: Re: IP Prefix-list Question
Hi, lee:
1=0001
2=0010
4=0100
5=0101
so, /21 over the 4 route,
4.0/23 over the 4.0 and 5.0
1.0/23 over the 1.0 and 2.0
HTH
dillon
----- Original Message -----
From: "Lee Donald" <Lee.Donald@t-systems.co.uk>
To: "Dillon Yang" <gzdillon@hotmail.com>; "Sundar Palaniappan"
<sundarp@gmail.com>
Cc: "Group Study" <ccielab@groupstudy.com>
Sent: Tuesday, March 29, 2005 11:48 PM
Subject: RE: IP Prefix-list Question
> Guys,
>
> I have tried this and it only lets subnets 4 & 5 in ?
>
> Also I was after the methlogy behind it so I can work it out for myself,
you
> just telling me the answer is only part of it.
>
> I don't quite understand the /23 and the le 24 ge 24 bits ?
>
>
>
> -----Original Message-----
> From: Dillon Yang [mailto:gzdillon@hotmail.com]
> Sent: 29 March 2005 16:41
> To: Sundar Palaniappan
> Cc: Group Study
> Subject: Re: IP Prefix-list Question
>
> Yes, Sundar:
>
> The task is just the SIX routes!
> so feel free.
> I think you'd not overthink the unknown subnet as 3, 6, 7.
> Any expert advice?
>
> HTH
> dillon
>
>
> ----- Original Message -----
> From: "Sundar Palaniappan" <sundarp@gmail.com>
> To: "Philippe Couture" <philippecouture@gmail.com>
> Cc: <ccielab@groupstudy.com>; <Lee.Donald@t-systems.co.uk>
> Sent: Tuesday, March 29, 2005 11:28 PM
> Subject: Re: IP Prefix-list Question
>
>
> > Dillon,
> >
> > You are allowing subnets 3, 6, 7 that aren't part of the requirment.
> >
> > Lee's requirement is minimum number of lines to be used. Your solution
> > would be correct if only one line is to be used to accomplish that.
> >
> > Not sure if Cisco would consider your solution correct.
> >
> > --Sundar Palaniappan
> >
> >
> > On Tue, 29 Mar 2005 10:23:04 -0500, Sundar Palaniappan
> > <sundarp@gmail.com> wrote:
> > > My bad.
> > >
> > > Last statement should be,
> > >
> > > ip prefix-list cisco permit 192.54.4.0/23 ge 24 le 24
> > >
> > > What you are doing is, you are permiting everything after
> > > 192.54.4.0/23 but the subnet mask has to be 24 bits always.
> > >
> > > If you don't use le 24 then you are allowing prefixes with shorter
> > > mask i.e .25, .26 etc to be advertised.
> > >
> > > In the lab, I wouldn't take a chance and just nail it down.
> > >
> > > HTH,
> > > Sundar Palaniappan
> > >
> > >
> > > On Tue, 29 Mar 2005 10:03:43 -0500, Philippe Couture
> > > <philippecouture@gmail.com> wrote:
> > > > Sundar,
> > > >
> > > > Wouldn't the third line need to be "ip prefix-list cisco permit
> > > > 192.54.4.0/23 ge 24" ?
> > > >
> > > > I could be wrong but I think that since you don't care about the
24th
> > > > bit (i.e. you want to match .4 and .5), you would use a mask length
of
> > > > 23, and the "ge 24" says to use prefix lengths of 24 or more. If you
> > > > want to really only allow 24 and nothing longer, you would also need
> > > > to add "le 24".
> > > >
> > > > Phil
> > > >
> > > >
> > > > On Tue, 29 Mar 2005 09:54:59 -0500, Sundar Palaniappan
> > > > <sundarp@gmail.com> wrote:
> > > > > Lee,
> > > > >
> > > > > Or you could you configure
> > > > >
> > > > > ip prefix-list cisco permit 192.54.1.0/24
> > > > > ip prefix-list cisco permit 192.54.2.0/24
> > > > > ip prefix-list cisco permit 192.54.4.0/24 ge 23
> > > > >
> > > > > Either way you need 3 statements atleast.
> > > > >
> > > > > HTH,
> > > > > Sundar Palaniappan
> > > > >
> > > > > On Tue, 29 Mar 2005 15:19:12 +0100, Lee Donald
> > > > > <Lee.Donald@t-systems.co.uk> wrote:
> > > > > > I'm having trouble understanding IP Prefix-lists can anybody
> clarify this
> > > > > > for me?
> > > > > >
> > > > > > I have this question; use a prefix list with the minimum amount
of
> lines to
> > > > > > allow 1,2,4,5 networks in.
> > > > > >
> > > > > > 192.54.1.0/24
> > > > > >
> > > > > > 192.54.2.0/24
> > > > > >
> > > > > > 192.54.4.0/24
> > > > > >
> > > > > > 192.54.5.0/24
> > > > > >
> > > > > > 192.54.21.0/24
> > > > > >
> > > > > > 192.54.22.0/24
> > > > > >
> > > > > > I have 3 lines, 2 denying 21, and 22, the other allowing
> everything.
> > > > > >
> > > > > > Is this the minimum?, if not why not?
> > > > > >
> > > > > > Thanks in advance for your help.
> > > > > >
> > > > > > Regards
> > > > > >
> > > > > > Lee Donald.
> > > > > >
> > > > > >
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