From: Ronald Johnson (ronbob@xxxxxxx)
Date: Mon Mar 20 2000 - 16:14:11 GMT-3
I am having some trouble with access list and distribute-list questions that
ask you to filter a specific range of network or host addresses. Reading
through Caslow's book I ran into a section entitled "A Suggested Approach to
Constructing Access-lists that Manipulate a Range of IP and Decnet
Addresses" (Page 677). Caslow proceeds to describe what seems like the most
convoluted and drawn-out process to determine specific masks that allow you
to filter hosts on a very granular basis. Caslow's method asks you to put
together a number chart that shows all of the subnet borders in a huge
chart. e.g.
128
64 192
32 96 160 224
16... and so on
Trying to write this out during the lab exam would probably kill 15 minutes
of your time..
Not only that, the chart is only a beginning. Caslow's method is so
complicated and time consuming, it leads me to wonder if there is an easier
and quicker way to create these types of access lists masks..
Caslow Example:
Q: Permit hosts 10.10.10.40 through 49 to be permitted network access while
blocking all others.
A: access-list 10 permit 10.10.10.40 0.0.0.7
access-list 10 permit 10.10.10.48 0.0.0.1
Is it just me? Is his formula actually fast and simple and I am simply
lacking the
gray cell power? :D
I have had a very hard time finding another tutorial or shortcut for this.
Anyone
have a better method out there? I would really appreciate your time in
responding.
Thanks!
-Ron
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