If this is a default subnet mask, then it would be a class C subnet mask. If you are subnetting a network and this is not the default subnet mask, then it could be either a class A or class B.
Seems to me, I'm still learning, that the Class D subnet mask would be 224.0.0.0 or 1110 0000.0000 0000.0000 0000.0000 0000 in binary. The Internet has been using classless subnets for a while now, so it may not be as relevant as it once was.
The default subnet would be 255.0.0.0 (class A)
The address you gave is not an IP address; it has the appearance of a subnet mask. It could be a class A or class B subnet mask.
Look at the first octet value and check the corresponding range. 1-126 class A, subnet mask 255.0.0.0 128-191 class B, subnet mask 255.255.0.0 192-223 class C, subnet mask 255.255.255.0
The default subnet masks per class are: class A 255.0.0.0 class B 255.255.0.0 class C 255.255.255.0
255.0.0.0The default subnet mask of a class A network is 255.0.0.0
The octets are different - a class a is 255.0.0.0 and a class C is 255.255.255.0 for a default subnet mask. Of course, if you are subnetting then this doesn't apply.
The no. of IP's that can be assigned to single computer depends on the subnet mask. if the subnet mask is of A class then the IP's assigned can be 16777216. If the subnet mask is of B class then the no. of IP's that can be assigned is 65536. And if the subnet mask is of C class then the IP's assigned can be 254.
The default subnet mask would be 255.255.0.0 for a class B address.
Class A default is 255.0.0.0 Class B default is 255.255.0.0 Class C default is 255.255.255.0
by default it is 255.255.255.0