A network designer needs each subnet to provide exactly six usable host addresses, with no addresses wasted beyond the network and broadcast addresses. Which IPv4 prefix length meets this requirement?
- A/29 Correct
- B/27
- C/28
- D/30
Why A is correct: A /29 leaves three host bits, so two to the third power is eight addresses, and subtracting the network and broadcast addresses leaves exactly six usable hosts.
Why B is wrong: A /27 leaves five host bits, giving 32 addresses and 30 usable hosts; tempting if you stop at the host-bit field, but it is far larger than six.
Why C is wrong: A /28 leaves four host bits, giving 16 addresses and 14 usable hosts; tempting if you miscount by a single host bit, but it doubles the size needed.
Why D is wrong: A /30 leaves two host bits, giving four addresses and two usable hosts, the point-to-point size; tempting but it supplies only two hosts, not six.