For the IPv4 address 192.168.10.77/26, which are the network and broadcast addresses?

• A. Network 192.168.10.0; Broadcast 192.168.10.63
• B. Network 192.168.10.128; Broadcast 192.168.10.191
• C. Network 192.168.10.64; Broadcast 192.168.10.127
• D. Network 192.168.10.192; Broadcast 192.168.10.255

Answer: (C)

Subnetting with a /26 mask creates blocks of 64 addresses in the last octet. Each block starts at a network address and ends at a broadcast address, with the addresses in between assigned to hosts.

For 192.168.10.77/26, the last octet blocks are 0–63, 64–127, 128–191, and 192–255. The address 77 falls in the 64–127 block, so its network address is 192.168.10.64 and its broadcast address is 192.168.10.127. This is why those two addresses are the network and broadcast for this subnet.

The other blocks would have network/broadcast pairs of 192.168.10.0/26 (network 192.168.10.0, broadcast 192.168.10.63), 192.168.10.128/26 (network 192.168.10.128, broadcast 192.168.10.191), and 192.168.10.192/26 (network 192.168.10.192, broadcast 192.168.10.255).