How many addresses are available in a subnet with a /30 prefix length?

In a subnet with a /30 prefix length, the subnet mask is 255.255.255.252. This configuration allows for 4 total IP addresses within the subnet.

The calculation is based on the formula for determining the number of addresses available in a subnet, which is 2 raised to the power of the number of host bits. For a /30 prefix, there are 2 bits left for host addresses (since a standard IPv4 address has 32 bits total). Therefore, the calculation is:

2^(32 - 30) = 2^2 = 4

These 4 addresses consist of:

1. The network address (which identifies the subnet itself and cannot be assigned to a host).

2. Two usable host addresses (which can be assigned to devices within the subnet).

3. The broadcast address (which is used to communicate with all devices on the subnet).

Hence, while only 2 addresses can be assigned to hosts, the total number of addresses available in that subnet is indeed 4, confirming that the choice of 4 is accurate.