Final answer:
The default subnet mask for a Class A network is 255.0.0.0, facilitating a large number of host addresses suitable for very large networks.
Step-by-step explanation:
The default subnet mask for a Class A network is 255.0.0.0. In IP networking, a subnet mask is used to divide the IP address into a network and host component. Class A networks are designated for use by very large networks, such as those used by internet service providers and large international organizations, and can support a massive number of individual host addresses.
A default subnet mask for Class A is designed to accommodate this by using only the first octet for network identification and leaving the remaining three octets for host addresses.