County courts needs an internal-only address plan for a SCADA island that must not use public Internet space. Which block is appropriate private IPv4 addressing?
Select an answer to reveal the explanation.
Short Explanation
172.16 through 172.31 is one of the big RFC1918 neighborhoods — perfect for an internal SCADA island. The other choices look like documentation or public-ish space, not private campus addressing.
Full Explanation
County courts needs an internal-only address plan for a SCADA island that must not use public Internet space. Among the choices, 172.16.0.0/12 is an RFC1918 private block (172.16.0.0 through 172.31.255.255) and is therefore appropriate for an air-gapped or internally routed SCADA design. It provides ample room to subnet SCADA cells, historian VLANs, and management networks without consuming public IPv4.
8.8.8.0/24 is public space associated with well-known Internet DNS addressing and must not be used as internal SCADA numbering. 198.51.100.0/24 and 203.0.113.0/24 are documentation/TEST-NET ranges (RFC 5737) intended for examples and documentation, not production private campus addressing; they are also not the RFC1918 private set.
Exam caveat: know the three RFC1918 blocks by prefix (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16) and distinguish them from documentation nets and public DNS/provider space. “Looks private” is not enough—check the RFC category.
Operational check for the courts SCADA island: allocate subnets from 172.16.0.0/12, ensure no default route to the Internet (or strict firewall deny), and verify that border filters drop 172.16/12 toward public peers. Label the addressing plan as RFC1918-only so future techs do not “borrow” 8.8.8.0/24 for convenience.