A server administrator is configuring a private subnet for an application expected to grow to 48 hosts. What CIDR netmask should be used for the least number of unused addresses?

When determining the appropriate CIDR netmask for a private subnet that will accommodate 48 hosts, it's essential to consider how many usable addresses each subnet size provides.

A CIDR notation indicates how many bits are used for the network portion of an IP address. The remaining bits are allocated for host addresses. The formula to calculate the number of usable addresses is 2^(32 - n) - 2, where n is the number of bits used for the network. The subtraction of two accounts for the network and broadcast addresses.

For a /26 netmask:

• This uses 26 bits for the network, leaving 6 bits for hosts (32 - 26 = 6).

• This gives 2^6 = 64 total addresses.

• Subtracting the 2 reserved addresses (network and broadcast) yields 62 usable addresses.

This is sufficient to accommodate the 48 hosts expected for the application, providing ample room for future growth without resulting in excessive waste of IP addresses. Using a /26 netmask optimally balances the need for available addresses and minimizes the number of unused addresses for this requirement.

In contrast, larger networks like /25 would provide more addresses than necessary and still have some unused, while smaller networks like