access list wild mask

[farhan.ahmed]

how to calculate the wild mask for access list

what would be the wildmask of a 172.16.0.0 /16

if we want to block 172.16.1.0 -172.16.240.0 address range

[ammar]

Try this, I think this may be it.

access-list 100 deny ip 172.16.0.0 0.0.15.255 any log-input

Basically, every bit with a 0 will be checked and the 1's should be allowed.

Let me know if this is wrong.

[roger.xu]

hi, if you want to block 172.16.1.0 -240.0, it is impossible to write it in one access-list. because

it is not in one range. you can use

172.16.0.0 0.0.127.255 as one range, then delete

172.16.0.0 and add the rest.