From: aansar@sscomp.com.sg
Date: Wed Oct 23 2002 - 03:21:20 GMT-3
you check binary equivalent and compare the matching bit..
as u know LOGICAL OR (between ip address and mask you supply) used by
access list to decide whether to permit or deny
you write the binary equivalent of 192.168.2.0 , 192.168.4.0 you can
observe that last bit is always zero
XOR truth table
so you have to access list to check the last bit and ignore all other 7
bits , so it is 1111-1110 , which is equivalent to 254
but u mentioned access-list 3 deny 192.168.1.0 0.0.254.255 which is wrong , it should be 192.168.0.0 0.0.254.255 to filter the
even subnets , if you do xor you can find it out why it is wrong.. you
want to match the with zero not with 1 ..
hope this help
aa
"Fan Shan" <fansh@publicf.bta.net.cn>
Sent by: nobody@groupstudy.com
10/23/2002 01:31 PM
Please respond to "Fan Shan"
To: "Ccielab@Groupstudy.Com" <ccielab@groupstudy.com>
cc:
Subject: How to understand this distribution list?
router ospf 1
distribution-list 3 out
access-list 3 deny 192.168.1.0 0.0.254.255
access-list 3 permit any
What will it do?
How can it advertise only even route like 192.168.2.0, 192.168.4.0,...
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