200-150 · Question #68
Which three statements about IPv6 prefixes are true? (Choose three.)
The correct answer is A. FF00:/8 is used for IPv6 multicast. B. FE80::/10 is used for link-local unicast. C. FC00::/7 is used in private networks.. IPv6 reserves specific prefixes for multicast (FF00::/8), link-local unicast (FE80::/10), and unique local (private) addresses (FC00::/7). Understanding these prefix boundaries is essential for IPv6 addressing.
Question
Which three statements about IPv6 prefixes are true? (Choose three.)
Options
- AFF00:/8 is used for IPv6 multicast.
- BFE80::/10 is used for link-local unicast.
- CFC00::/7 is used in private networks.
- D2001::1/127 is used for loopback addresses.
- EFE80::/8 is used for link-local unicast.
- FFEC0::/10 is used for IPv6 broadcast.
How the community answered
(60 responses)- A95% (57)
- D2% (1)
- E3% (2)
Why each option
IPv6 reserves specific prefixes for multicast (FF00::/8), link-local unicast (FE80::/10), and unique local (private) addresses (FC00::/7). Understanding these prefix boundaries is essential for IPv6 addressing.
FF00::/8 is the reserved multicast range in IPv6 as defined by RFC 4291; all addresses beginning with FF are multicast and replace IPv4 broadcast and multicast functions.
FE80::/10 is the link-local unicast prefix per RFC 4291; addresses in this range are automatically assigned to interfaces and are only valid on a single network segment, never forwarded by routers.
FC00::/7 defines the unique local address (ULA) space per RFC 4193, covering both FC00::/8 and FD00::/8, and is used for private IPv6 communication analogous to RFC 1918 in IPv4.
2001::1/127 is a global unicast address format used for point-to-point links per RFC 6164; the IPv6 loopback address is ::1/128, not this prefix.
FE80::/8 uses an incorrect prefix length - the actual link-local prefix is FE80::/10, which spans FE80:: through FEBF::, not just /8.
FEC0::/10 was the deprecated site-local address prefix (RFC 3879) and was never used for broadcast; IPv6 has no broadcast addressing at all.
Concept tested: IPv6 special-purpose address prefix ranges
Source: https://www.rfc-editor.org/rfc/rfc4291#section-2.4
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