From: Jalaluddien (mjalal@sejeltech.com)
Date: Tue Feb 21 2006 - 02:35:15 GMT-3
Hi
I guess the below statement is correct for odd-numbers
Access-list 101 permit ip any 218.18.1.0 0.0.254.255
Correct me if I am wrong.
jalal
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Radoslav Vasilev
Sent: Monday, February 20, 2006 6:01 PM
To: Popgeorgiev Nikolay
Cc: Daniel O'Sheedy; Emil Patel; ccielab@groupstudy.com
Subject: Re: Permitting odd and even routes??
Hi,
If you let me concentrate on the odd-number ACL, as it is more interesting:
Let's also get further and assume that your task requires from us to make
sure we're permitting only the odd-numbered networks 218.18.1.0 and
218.18.3.0 as opposed to all odd-number /24 subnets. As this makes the
things even more interesing. Let also presume we have only one line to
achive this:
access-list 101 permit ip any 218.18.1.0 0.0.2.255
That's it!
A bit more detail on this:
218.18.1.0 has thrid octed looking in binary : 0000.0001
218.18.3.0 has third octed looking in binary : 0000.0011
it is obvious that the least-significant bit there shouldn't change from 1
as we want ot restrict the ACL to those two networks only, it is obvious
that we also have th first 6bits (most significat bits) fixed.
That leave us with an ACL looking again in binary like this (for the third
octed of course): 0000.0010 = 2
and the whole inverse mask 0.0.2.255
Cheers,
-rado
On 2/16/06, Popgeorgiev Nikolay <nikolay.popgeorgiev@siemens.com> wrote:
>
> Hi,
>
> According to my knowledge if you use
>
> 212.18.0.0 0.0.254.255 you can allow networks like:
>
> 212.18.0.0/30
> 212.18.0.4/30
> 212.18.2.0/30
> 212.18.2.4/29
> 212.18.2.12/28
>
> and so on... So you can match networks not only /24 but
> other
>
> But if you have 212.18.0.0 0.0.254.0
>
> you have to keep tha last octed to 0 always
> 212.18.0.0
> 212.18.2.0
> 212.18.4.0
>
> Correct me if I am wrong
>
> Best,
> Nick
>
>
>
> -----Original Message-----
> From: Daniel O'Sheedy [mailto:dansheedy@gmx.net]
> Sent: Thursday, February 16, 2006 9:14 AM
> To: Emil Patel; ccielab@groupstudy.com
> Subject: Re: Permitting odd and even routes??
>
> Hi!
>
> There is a great little tool for free from here:
>
> http://www.boson.com/FreeUtilities.html
>
> Its called the IP Subnet Calculator, and it has the Wildcard Mask Checker
> built in. So you can put in the subnet you want to play with, and then
> play
> with the mask to check different results.
>
> If you want to just allow even, then you would use something like this:
>
> allow 218.18.0.0 0.0.254.255 (allow just the even through)
> deny any (deny the rest)
>
> If you want to allow just the odd, then you could use something like this:
>
> deny 218.18.0.0 0.0.254.255 (deny the even routes... they are not
> interesting)
> allow 218.18.0.0 0.0.255.255 (allow the 'rest' of the routes in that
> range
> through... which are by now only the odds)
>
> Have a play with the tool, and it comes easier with practice.
>
> Dan
>
>
>
>
> ----- Original Message -----
> From: "Emil Patel" <emilpatel@hotmail.com>
> To: <ccielab@groupstudy.com>
> Sent: Wednesday, February 15, 2006 11:47 PM
> Subject: Permitting odd and even routes??
>
>
> >I have following rip routes being learned from the BB routers:
> >
> >
> >
> > 218.18.0.0/24
> >
> > 218.18.1.0/24
> >
> > 218.18.2.0/24
> >
> > 218.18.3.0/24
> >
> >
> >
> > If I just want allow odd or even numbered routes based on 3rd octet,
> here
> > what I have in my config:
> >
> >
> >
> > For odd routes:
> >
> > Access-list 10 permit 212.18.0.0 0.0.255.255
> >
> >
> >
> > For even routes:
> >
> > Access-list 10 permit 212.18.0.0 0.0.254.255
> >
> >
> >
> > Is this correct?
> >
> >
> >
> > Emil
> >
> > _______________________________________________________________________
> > Subscription information may be found at:
> > http://www.groupstudy.com/list/CCIELab.html
>
> _______________________________________________________________________
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>
> _______________________________________________________________________
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