From: Shine Joseph (shinepjoseph@iprimus.com.au)
Date: Wed Apr 09 2008 - 18:12:26 ART
Matt,
You missed one - 4.4.4.20
I work out this way:
Map the values to the corresponding bits
000 - 0+0+0 = 0
001 - 0+0+4 = 4
010 - 0+8+0 = 8
011 - 0+8+4 = 12
100 - 16+0+0 = 16
101 - 16+0+4 = 20
110 - 16+8+0 = 24
111 - 16+8+4 = 28
HTH,
Shine
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Matt
Bentley
Sent: Thursday, 10 April 2008 6:59 AM
To: Cisco certification
Subject: Understanding ACLs in your head
Hi GS:
I am trying to understand how to apply access lists to match multiple
addresses. I have basically created a local policy route to NULL0, so I can
track which addresses I Ping match the ACL I called to be matched in the
ACL. I have seen a few patterns, but this one being the main one
4.4.4.0 0.0.0.28
To Make 28, I need the following: 16,8,4 (zero is included because this is
the "base" address
Adding the various combinations of 16,8,and 4 give you these numbers:
16+8=24
16+8+4=28
4+8=12
So, the hosts that ACL would match would be as follows:
4.4.4.0
4.4.4.4
4.4.4.8
4.4.4.16
4.4.4.12
4.4.4.24
4.4.4.28
Is this correct for all ACLs?
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