Which type of network masking is used when Cisco IOS access control lists are configured?
A.
extended subnet masking
B.
standard subnet masking
C.
priority masking
D.
wildcard masking
Explanation:
Masks are used with IP addresses in IP ACLs to specify what should be permitted and denied.
Masks in order to configure IP addresses on interfaces start with 255 and have the large values on
the left side, for example, IP address 209.165.202.129 with a 255.255.255.224 mask. Masks for IP
ACLs are the reverse, for example, mask 0.0.0.255. This is sometimes called an inverse mask or
a wildcard mask. When the value of the mask is broken down into binary (0s and 1s), the resultsdetermine which address bits are to be considered in processing the traffic. A 0 indicates that the
address bits must be considered (exact match); a 1 in the mask is a “don’t care”.
Reference: http://www.cisco.com/c/en/us/support/docs/security/ios-firewall/23602-
confaccesslists.html