Which IPv6 prefix is reserved for private (local) addressing?

• A. fe80::/10
• B. fc00::/7
• C. 2000::/3
• D. ff00::/8

Answer: (B)

Private IPv6 addressing uses Unique Local Addresses, which are designated by the fc00::/7 prefix. This space is reserved for private, internal use within an organization and is not meant to be routable on the public Internet. It lets networks use locally assigned addresses and connect private sites without conflicting with global addresses. In practice, addresses often fall under fd00::/8 as locally assigned within that block, but the formal private-space prefix is fc00::/7.

The other prefixes serve different purposes: fe80::/10 is for link-local addresses used only on a single network link and not intended for private-wide routing; 2000::/3 is global unicast space for publicly routable addresses; ff00::/8 is multicast.