Which host address patterns are reserved in IPv4?

• A. 0.0.0.0 and 255.255.255.255
• B. 0.0.0.0 and 0.0.0.0
• C. 255.255.255.255 and 255.255.0.0
• D. 127.0.0.1 and 0.0.0.0

Answer: (A)

In IPv4, some addresses exist for special purposes and aren’t used as regular host addresses. The pair 0.0.0.0 and 255.255.255.255 are the two well-known patterns that are reserved for these special roles: 0.0.0.0 is the unspecified address used when a device doesn’t yet know its own address or when signaling “this host,” and 255.255.255.255 is the limited broadcast address used to reach all hosts on the local network segment. Routers do not forward this broadcast, it stays on the local link.

Other options mix addresses that have different reserved roles or aren’t valid host patterns in the same sense. For example, 127.0.0.1 is the loopback address used to reach the local host, which is a different kind of reserved purpose, and the pair as a whole isn’t the commonly cited “host address patterns” reserved for initial addressing and local broadcast. 255.255.0.0 isn’t a host address pattern; it’s typically a subnet mask, not a destination host address.