Convert the CIDR notation 192.168.10.0/26 to determine its first usable IP, last usable IP, and the broadcast address.

Convert the CIDR notation 192.168.10.0/26 to determine its first usable IP, last usable IP, and the broadcast address.

• A. First usable: 192.168.10.1; Last usable: 192.168.10.62; Broadcast: 192.168.10.63.
• B. First usable: 192.168.10.0; Last usable: 192.168.10.63; Broadcast: 192.168.10.63.
• C. First usable: 192.168.10.1; Last usable: 192.168.10.63; Broadcast: 192.168.10.62.
• D. First usable: 192.168.10.2; Last usable: 192.168.10.61; Broadcast: 192.168.10.62.

Answer: (A)

Understanding how CIDR blocks define address ranges is the key. A /26 subnet means 64 addresses per block (since 2^6 = 64), with the network portion fixed and the last 6 bits available for hosts. Starting at 192.168.10.0, the first block runs from 192.168.10.0 to 192.168.10.63. In every subnet, the network address is the first address, and the broadcast address is the last. Therefore, 192.168.10.0 is the network address, 192.168.10.63 is the broadcast, and the usable host addresses lie in between: 192.168.10.1 through 192.168.10.62. This means the first usable is 192.168.10.1, the last usable is 192.168.10.62, and the broadcast is 192.168.10.63. The other options place either the network or broadcast in the wrong positions or treat unusable addresses as usable.

Understanding how CIDR blocks define address ranges is the key. A /26 subnet means 64 addresses per block (since 2^6 = 64), with the network portion fixed and the last 6 bits available for hosts. Starting at 192.168.10.0, the first block runs from 192.168.10.0 to 192.168.10.63. In every subnet, the network address is the first address, and the broadcast address is the last. Therefore, 192.168.10.0 is the network address, 192.168.10.63 is the broadcast, and the usable host addresses lie in between: 192.168.10.1 through 192.168.10.62. This means the first usable is 192.168.10.1, the last usable is 192.168.10.62, and the broadcast is 192.168.10.63. The other options place either the network or broadcast in the wrong positions or treat unusable addresses as usable.