How many usable hosts does a /30 subnet provide, and what is it typically used for?

• A. 4 usable hosts; typically used for broadcast networks.
• B. 2 usable hosts; typically used for point-to-point links.
• C. 1 usable host; typically used for loopback.
• D. 30 usable hosts; typically used for small LANs.

Answer: (B)

The main concept is how many host addresses a given subnet can provide. A /30 uses a 255.255.255.252 mask, which yields four addresses in the subnet: one network address, two usable host addresses, and one broadcast address. After reserving network and broadcast, you’re left with exactly two usable hosts. This tiny address space is ideal for point-to-point links between two devices, such as two routers on a WAN link, where only two IPs are needed and wasting addresses would be inefficient. The other options either count too many usable hosts, describe an unrelated use, or mix up what a /30 is typically used for.