wild card masks

[aguila3380]

If you addresses had addresses 192.168.1.1/24 through 192.168.1.254/24 (192.168.1.0/24 being your subnet ID, and 192.168.1.255/24 being your subnet broadcast), what would be the wild card mask in your ACL(Access Control List) to permit only addresses 192.168.1.5/24 through 192.168.1.13/24, and how would/did you calculate it.(Note: I already know about subtracting 255 from each octet.)

[Chris Deren]

In order to create an access list with course address of the range 192.168.1.5 - 13 you need to brake it up in three conditions:

Forth octet

000001 01 192.1668.1.5

000001 10 192.1668.1.6

000001 11 192.1668.1.7

Wildcard mask = 0.0.0.3

000010 00 192.1668.1.8

000010 01 192.1668.1.9

000010 10 192.1668.1.10

000010 11 192.1668.1.11

Wildcard mask = 0.0.0.3

0000110 0 192.168.1.12

0000110 1 192.168.1.13

Wildcard mask = 0.0.0.1

So, your access list:

access-list 1 permit 192.168.1.5 0.0.0.3

access-list 1 permit 192.168.1.8 0.0.0.3

access-list 1 permit 192.168.1.12 0.0.0.1

Hope this helps,

Chris

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