Which IPv6 address block is reserved for private use and is not globally routable?

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

Answer: (C)

IPv6 private-use addressing is provided by Unique Local Addresses (ULA). These use the fc00::/7 prefix and are intended for internal networks, not for global routing on the Internet. The /7 block encompasses the private space, meaning addresses within fc00::/7 are not meant to be reachable from the global Internet. Within that range, fd00::/8 is commonly used for locally assigned ULAs, but the important takeaway for this question is that the private-use block is fc00::/7.

In contrast, fe80::/10 is reserved for link-local addresses, which are used for communication on a single network segment and are not routable beyond the link. The 2000::/3 space is for global unicast addresses and is routable on the Internet, not private. And ff00::/8 is multicast, not unicast.