Final answer:
The default subnet mask for an IP address depends on the class of the network it belongs to. Class A uses 255.0.0.0, Class B uses 255.255.0.0, and Class C uses 255.255.255.0.
Step-by-step explanation:
The default subnet mask for an IP address depends on the class of the network it belongs to. There are five classes of IP addresses: A, B, C, D, and E. The classes differ in the number of network and host bits, which determine the default subnet mask.
For a Class A address, the default subnet mask is 255.0.0.0, which means that the first octet (8 bits) is used for the network address, and the remaining three octets (24 bits) are available for hosts.
For a Class B address, the default subnet mask is 255.255.0.0, which means that the first two octets (16 bits) are used for the network address, and the remaining two octets (16 bits) are available for hosts.
For a Class C address, the default subnet mask is 255.255.255.0, which means that the first three octets (24 bits) are used for the network address, and the last octet (8 bits) is available for hosts.