What is the netmask for a /8 prefix length?

The netmask for a /8 prefix length is 255.0.0.0. In the context of subnetting, the prefix length indicates how many bits are used for the network portion of the address. A /8 prefix means that the first 8 bits of the address are dedicated to the network part, while the remaining 24 bits are available for host addresses within that network.

The notation is derived from the fact that a standard IPv4 address consists of 32 bits. In a /8 network, the first 8 bits are set to '1', which corresponds to the decimal value of 255 when converted to a dotted-decimal format. The remaining bits in the netmask would be '0's, making the rest of the octets equal to zero (0). Thus, the complete netmask is represented as 255.0.0.0, clearly showing that only the first octet is used for the network, while the other three octets allow for host assignment.

Understanding this format is crucial for network design and IP addressing, as it defines the size of the network and how many hosts can be assigned within that network.