(Thanks to Bob Hennigan, and Steve Perry, CIS Instructors at Central New Mexico Community College.)
22 Feb 2014
kenglong@gmail.com
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Binary reference chartsaccess-list 1 permit [address_to_check] [wildcard_used_to_check]We need to find the "address-to-check" and the "wildcard-used-to-check".
1.2.3.4
5.6.7.8
9.10.11.12
13.14.15.16
1.2.3.4 | 00000001 00000010 00000011 00000100 |
5.6.7.8 | 00000101 00000110 00000111 00001000 |
9.10.11.12 | 00001001 00001010 00001011 00001100 |
13.14.15.16 | 00001101 00001110 00001111 00010000 |
00000001 00000010 00000011 00000000
Convert that to decimal and we have:1.2.3.0
00001100 00001100 00001100 00011100Convert that to binary and we get:
12.12.12.28This is our wildcard-used-to-check. Plugging the two results into our ACL gives us the most specific wildcard mask possible and the address which represents the original addresses.
access-list 1 permit 1.2.3.0 12.12.12.28
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