From: Tony Olzak (aolzak@xxxxxxxxxxxxxxxxxxx)
Date: Fri Dec 01 2000 - 12:50:37 GMT-3
DJ,
It's not a bit swap. That's a typo, should be "C" instead of "D". What
you are doing is like in supernetting IP, you are moving the bits in
the mask to the left to summarize a couple of networks. The networks
0-3 can be made using the bits 0000, 0001, 0010, and 0011. Your
original IPX mask in an IPX network is all ones, or FFFFFFFF. Move the
bits two to the left to summarize the last two bits and you have
FFFFFFFC, or 1111 1111 1111 1111 1111 1111 1111 1100. Note the last
two bits are empty.
Link this to IP for a better understanding. You have networks
192.168.1.0/30, 192.168.1.4/30, 192.168.1.8/30, and 192.168.1.12/30.
/30 is 252, or 11111100
Use a network of 192.168.1.0 255.255.255.240 to summarize. The 240
means 11110000. You've moved the bits two to the left to summarize
0-15 (16 was your next network number).
Do I hear any "AHH's" yet? =)
Tony
l Message -----
From: D. J. Jones
To: Tony Olzak
Sent: Friday, December 01, 2000 10:17 AM
Subject: Re: IPX Masks
Tony, I think I understand the second example you give for summarizing
0-7 using FFFFFFF8, but I fail
to understand the first example summarizing 0-3 using FFFFFFFD? Did
you do a bit swap from
0011 to 1100? If so, why would we not do a bit swap on the second
example from 1000 to 0001?
Thanks..dj
----- Original Message -----
From: Tony Olzak
To: damien ; ccielab@groupstudy.com
Sent: Thursday, November 30, 2000 6:57 PM
Subject: Re: IPX Masks
This is a network summary mask that works just like a standard IP
subnet mask. You just have to convert to binary to figure it out. The
all "F"s means the equivalent of a /32 mask in IP.
In your last nibble:
0 = 0000
1 = 0001
2 = 0010
3 = 0011
4 = 0100
5 = 0101
In your scenario, since you only want to deny up to network 11110005,
you can only summarize 0-3 in one statement. Otherwise you would
summarize 0-7 in a single statement.
Your statement would be:
access-list 1200 deny 11110000 FFFFFFFD
The "D" stands for "1100", which means you are summarizing networks
0-3.
If you wanted 0-7 you would need to use "1000", or FFFFFFF8 as the IPX
mask.
Tony
----- Original Message -----
From: damien
To: ccielab@groupstudy.com
Sent: Thursday, November 30, 2000 2:37 PM
Subject: IPX Masks
Can anyone explain how IPX Masks work with IPX access lists for NLSP
redistribution and give some examples..............
Just as an example, I had the following range of IPX Networks
11110001....2....3...4 - 9 for example and I wanted to filter the
first 5....other than extering the following 5 lines, is it possible
with a single statement or at least less statements to do the same
job........????
access-lists 1200 deny 11110002 FFFFFFFF
access-lists 1200deny 11110002 FFFFFFFF
access-lists 1200 deny 11110002 FFFFFFFF
access-lists 1200 deny 11110004 FFFFFFFF
access-lists 1200 deny 11110005 FFFFFFFF
Any good sources of info........................
Thanks
Damien
"An expert is a man who has made all the mistakes which can be made,
in a narrow field" - Niels Bohr
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