How many usable IP addresses are there in a 23-bit subnet mask (255.255.254.0)?

In a 23-bit subnet mask, also represented as 255.255.254.0, the subnet mask allows for 23 bits to be used for the network portion and the remaining 9 bits for host addresses.

To determine the number of usable IP addresses in this subnet, we first need to calculate the total number of addresses available using the formula (2^n), where (n) is the number of bits allocated for hosts. In this case, (n) is 9, as there are 32 total bits (IPv4) minus 23 network bits.

Calculating (2^9) gives us 512 total addresses. However, within any subnet, two IP addresses are reserved. One is the network address (which identifies the subnet itself) and the other is the broadcast address (which is used to communicate with all devices on the subnet). This means that the number of usable IP addresses is (512 - 2), which equals 510.

Thus, the correct answer is indeed 510. Understanding how to account for the reserved addresses is crucial in subnetting; it ensures effective utilization of IP address space while enabling proper network functionality.