From: Devi Mallampalli (Devi.Mallampalli@chubb.com.au)
Date: Mon May 03 2004 - 05:15:20 GMT-3
Hi Group & Ken,
The trick I think here is to use "NCBB" ( non common bit boundary),
which is opposite to CBB which we normally use during
summarization/aggregation. For example in the first half of the
question, instead of 8 x 10.1.x.x prefix ACL commands for the following
networks, we can indeed derive similar result with 4 commands by picking
up NCBB on the 3rd octet and lock down the mask accordingly as stated
below.
8 networks : >>>>>>>
10.1.1.0 /24
10.1.2.0 /24
10.1.4.0 /24
10.1.8.0 /24
10.1.16.0 /24
10.1.32.0 /24
10.1.64.0 /24
10.1.128.0 /24
Condensed to 4 networks and at the same time allowing every thing else
>>>>>>
10.1.1.0 /24 00001010.00000001.00000001.00000000 /
11111111.1111111.11111111.0
10.1.2.0 /24 00001010.00000001.00000010. 00000000 /
11111111.1111111.11111111.0
10.1.1.0 / 0.0.1.255 >>>>>>>>>>>>>>
10.1.4.0 /24 00001010.00000001.00000100. 00000000 /
11111111.1111111.11111111.0
10.1.8.0 /24 00001010.00000001.00001000. 00000000 /
11111111.1111111.11111111.0
10.1.4.0 / 0.0.4.255 >>>>>>>>>>>>>>
10.1.16.0 /24 00001010.00000001.00010000. 00000000 /
11111111.1111111.11111111.0
10.1.32.0 /24 00001010.00000001.00100000. 00000000 /
11111111.1111111.11111111.0
10.1.16.0 / 0.0.16.255 >>>>>>>>>>>>
10.1.64.0 /24 00001010.00000001.01000000. 00000000 /
11111111.1111111.11111111.0
10.1.128.0 /24 00001010.00000001.10000000. 00000000 /
11111111.1111111.11111111.0
10.1.64.0 / 0.0.64.255 >>>>>>>>>>>>
Dev
-----Original Message-----
From: Kenneth Wygand [mailto:KWygand@customonline.com]
Sent: Monday, 3 May 2004 9:36 AM
To: ccielab@groupstudy.com
Subject: Quiz Question of the Day 20040502
Write an access list (ACL 10) using the _fewest_ number of lines that
denies _all_ of the following networks _without_ oversummarization and
permits all other networks.
10.1.1.0 /24
10.1.2.0 /24
10.1.4.0 /24
10.1.8.0 /24
10.1.16.0 /24
10.1.32.0 /24
10.1.64.0 /24
10.1.128.0 /24
10.1.1.0 /24
10.2.1.0 /24
10.4.1.0 /24
10.8.1.0 /24
10.16.1.0 /24
10.32.1.0 /24
10.64.1.0 /24
10.128.1.0 /24
If you really understand how access lists work, this one should be
easy... :)
Ken
This archive was generated by hypermail 2.1.4 : Wed Jun 02 2004 - 11:12:03 GMT-3