What is IP class and number of sub-networks if the subnet mask is 255.224.0.0?

The subnet mask 255.224.0.0 indicates a Class A network because the first octet is 255, matching the default boundary for Class A. To find the number of sub-networks, compare this mask to the default Class A mask (255.0.0.0). The second octet is 224, which converts to binary as 11100000. This shows 3 bits are used for subnetting beyond the default network portion. The number of sub-networks is calculated as 2 raised to the power of the subnet bits: 23 = 8.