A new network is being created to support 126 users.

To support 126 users, the subnet must provide at least 126 usable host addresses. In IPv4 subnetting, usable hosts are calculated as: (2^(host bits)) − 2, subtracting the network and broadcast addresses.

A /25 leaves 7 host bits (because 32 − 25 = 7). That yields 2^7 = 128 total addresses, and 128 − 2 = 126 usable—an exact fit and therefore the most efficient option listed.

A /24 provides 256 total addresses and 254 usable, which would waste more addresses than necessary. A /23 provides 512 total addresses and 510 usable—far more waste. A /26 leaves 6 host bits, giving 64 total addresses and 62 usable, which is not enough for 126 users.

The 10.2.2.0 address is within the private 10.0.0.0/8 range, so it’s appropriate for internal addressing. Therefore, 10.2.2.0/25 is the correct CIDR range for efficiently supporting 126 hosts.