More about ACLs

From: jfaure@sztele.com
Date: Sat May 10 2003 - 06:31:05 GMT-3


Hi all:

I'm having some troubles with acls. Imagine you have these networks:

199.172.1.0/24
199.172.2.0/24
199.172.4.0/24
199.172.5.0/24
199.172.6.0/24
199.172.8.0/24
199.172.21.0/24

And you must filter, with the minimun number of lines in the ACL, and only
permit the odd networks (at the third octect, this is ONLY the 1, 5 and
21, not each possible odd subnet). Then you could do so with a standard
access list like this:

access-list 99 permit 199.172.1.0 0.0.20.255

However, this access-list also allows networks like 199.172.1.0/25
199.172.1.0/26 , etc. Imagine you want to be more specific and to match the
network mask too. Then you'd need an extended acl that only allows /24.
But, anyone can suggest how to construct it, if it's possible?

Regards

Juan Faure Ferrer
email: jfaure@sztele.com

Lmnea de Negocio de Telematica y CC
Ingeniero de Integracisn de Redes y Sistemas
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