Which of the following is a private IPv4 address block within the 172 range?

Which of the following is a private IPv4 address block within the 172 range?

• A. 172.16.0.0/12
• B. 172.0.0.0/8
• C. 172.32.0.0/12
• D. 172.255.0.0/16

Answer: (A)

Private IPv4 addresses are set aside for internal networks and aren’t routable on the public Internet. RFC 1918 defines three private ranges: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Within the 172.x space, the private block is 172.16.0.0/12, which covers 172.16.0.0 through 172.31.255.255. So the address block 172.16.0.0/12 is the private 172-range block. The other options don’t fit because they either start outside the private window or span addresses outside the 172.16.0.0/12 range.

Private IPv4 addresses are set aside for internal networks and aren’t routable on the public Internet. RFC 1918 defines three private ranges: 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. Within the 172.x space, the private block is 172.16.0.0/12, which covers 172.16.0.0 through 172.31.255.255. So the address block 172.16.0.0/12 is the private 172-range block. The other options don’t fit because they either start outside the private window or span addresses outside the 172.16.0.0/12 range.