Cisco IOS Extended Access List changes destination network to 0.0.0.0

Question

I am trying to create named extended access-lists on Cisco IOS on an 800 series router, but it changes the destination network to 0.0.0.0.

Example:

ip access-list extended ACL-TEST
    permit tcp host 192.168.1.44 192.168.2.0 255.255.255.0 eq 44818
exit

is accepted with no errors, but then when I run "show access-lists" the output is:

Extended IP access list ACL-TEST
    10 permit tcp host 192.168.1.44 0.0.0.0 255.255.255.0 eq 44818

What am I doing wrong? Thanks.

Answer 1

Access lists do not use an ordinary subnet mask. They use a "wildcard " mask. A wildcard mask is the ones complement of the subnet mask. So 255.255.255.0 becomes 0.0.0.255