If the host portion of an IPv4 address is all 1s, what kind of address is it?

In IPv4 addressing, when the host portion of an address is completely filled with ones (1s), it signifies a broadcast address for that particular network. A broadcast address is used to send data to all possible devices within the same subnet. For example, if you have a network with a subnet mask of 255.255.255.0 (or /24), the broadcast address would be the last address in that subnet range. If the network address is 192.168.1.0, then the broadcast address would be 192.168.1.255, where the last octet (the host portion) consists of all 1s in binary (11111111).

This unique property allows devices on the same network to communicate simultaneously with all others without needing to specify individual IP addresses. In contrast, network addresses and private addresses serve different purposes, such as identifying the network itself or being used within private IP ranges, respectively. A gateway address refers to the routing device that connects networks, which does not correlate with having all 1s in the host portion either. Thus, the correct choice reflects the specific functionality of broadcast addresses in TCP/IP networking.