RE: Prefix-list

From: subodh.rawat@wipro.com
Date: Tue Oct 02 2007 - 05:43:11 ART


I think you are right. "0.0.0.0/0 ge 1" will permit everthing but
default-route 0.0.0.0/0 will be denied in next implicit statement.

Thanks Saul/Lim for correcting me. I think this is the true power of
Group Study of debating over topics and making full use of it.

Regards
Subodh

________________________________

From: Toh Soon, Lim [mailto:tohsoon28@gmail.com]
Sent: Tuesday, October 02, 2007 1:34 PM
To: Subodh Singh Rawat (WT01 - TELECOM SERVICE PROVIDER)
Cc: saul.arjona.bueno@gmail.com; sameh@bayanat.com.sa;
ccielab@groupstudy.com
Subject: Re: Prefix-list

Hi Subodh,

I have not labbed it to verify.

Nevertheless, if my understanding is correct, for "0.0.0.0/0 le 32", the
prefix length is as follows:

0 <= len <= 32

For "0.0.0.0/0 ge 1", prefix length is:

1 <= len <= 32

The prefix length of default route is 0. Thus IMHO, the "0.0.0.0/0 ge 1"
will not match the default route. It will be denied by the next implicit
deny statement. Do correct me if I'm wrong.

Thank you.

B.Rgds,
Lim TS

On 10/2/07, subodh.rawat@wipro.com <subodh.rawat@wipro.com> wrote:

        prefix-list 0.0.0.0/0 le 32 and 0.0.0.0/0 ge 1 have same effect,
i.e. To
        permit or deny any routes. While 0.0.0.0/0 is exact match of
default
        route.

        So below two configurations have same effect.

        Ip prefix-list MYLIST deny 192.168.1.0/24

        Ip prefix-list MYLIST permit 0.0.0.0/0 ge 1
        AND
        Ip prefix-list MYLIST deny 192.168.1.0/24 <
http://192.168.1.0/24 <http://192.168.1.0/24> >
        Ip prefix-list MYLIST permit 0.0.0.0/0 <http://0.0.0.0/0> le 32

        Hope this helps.

        Regards
        Subodh

        ________________________________

        From: Saul Arjona [mailto:saul.arjona.bueno@gmail.com]
        Sent: Tuesday, October 02, 2007 11:36 AM
        To: Subodh Singh Rawat (WT01 - TELECOM SERVICE PROVIDER)
        Cc: sameh@bayanat.com.sa; ccielab@groupstudy.com
        Subject: Re: Prefix-list

        If you use:

        Ip prefix-list MYLIST deny 192.168.1.0/24

        Ip prefix-list MYLIST permit 0.0.0.0/0 ge 1

        You would be denying 192.168.1.0/24 network and also de default
route
        0.0.0.0 and permitting everything else

        Since the task states that you deny 192.168.1.0/24 and permit
everything
        else I would use

        Ip prefix-list MYLIST deny 192.168.1.0/24
        Ip prefix-list MYLIST permit 0.0.0.0/0 le 32

        regards
        -Saul

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