RE: Overlapping with Access-lists

From: HP-France,ex2 ("SANCHEZ-MONGE,ANTONIO)
Date: Sun Mar 21 2004 - 10:10:55 GMT-3


The shortest list I can figure out without overlap is:

226.0.0.0 1.255.255.255
228.0.0.0 3.255.255.255
232.0.0.0 3.255.255.255
236.0.0.0 1.255.255.255
238.0.0.0 0.255.255.255

In fact 226.0.0.0 0 12.255.255.255 will exclude things like 227.x.x.x
228.x.x.x . It will not overlap, but will not include some ranges.

Cheers,
Ato.

-----Original Message-----
From: Ahmed Mustafa [mailto:ahmed.mustafa@sbcglobal.net]
Sent: domingo, 21 de marzo de 2004 3:47
To: ccielab@groupstudy.com
Subject: Overlapping with Access-lists

Can someone explain how to check for overlapping with the following
access-lists.

If the question is to allow the range of multicasting groups from 226.0.0.0-
238.255.255.255.

Can I write:

access-list 1 permit 226.0.0.0 0 12.255.255.255

It is mentioned that since the complete 16 block of multicast range is
224.0.0.0 239.255.255.255 the above access-list will overlap. I can't
figure it out how though.

226.0.0.0 11100010
227.0.0.0 11100011
228.0.0.0 11100100
229.0.0.0 11100101
230.0.0.0 11100110
231.0.0.0 11100111
232.0.0.0 11101000
233.0.0.0 11101001
234.0.0.0 11101010
235.0.0.0 11101011
236.0.0.0 11101100
237.0.0.0 11101101
238.0.0.0 11101110

How do we find the overlapping issues with the above binary format, and then
group them to proper access-lists commands.

Regards,

Ahmed



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