The default subnet mask of an IP address 192.168.10.10 is ______.
A.
255.0.0.0
B.
255.255.0.0
C.
255.255.255.0
D.
255.255.255.255
Explanation:
192.168.10.10 is a Class C IP address. A Class C IP address uses the first 24 bits for network
identification and the last 8 bits for host identification. The result is an IP address range from
192.0.0.1 through 223.225.225.225 and a default subnet mask of 255.255.255.0.
Incorrect Answers:
A: Class A IP addresses use the first 8 bits for network identification and the last 24 bits for host
identification. The result is an IP address range from 0.0.0.0 through 127.255.255.255 and a
default subnet mask of 255.0.0.0.
B: Class B IP addresses use the first 16 bits for network identification and the last 16 bits for host
identification. The result is an IP address range from 128.0.0.0 through 191.255.255.255 and adefault subnet mask of 255.255.0.0.
D: 255.255.255.255 is not a valid subnet mask as it uses all 32 bits for network identification,
leaving zero bits for host addresses.Reference:David Groth and Toby Skandier, Network+ Study
Guide (4th Edition), Sybex, Alameda CA, 2005, pp. 127-128.