200-101 · Question #121
Which of these represents an IPv6 link-local address?
The correct answer is A. FE80::380e:611a:e14f:3d69. IPv6 link-local addresses are identified by the FE80::/10 prefix (range FE80:: to FEBF::) and are used exclusively for communication on a single network segment.
Question
Options
- AFE80::380e:611a:e14f:3d69
- BFE80::280:512b:e14f:3d69
- CFEFE:0345:5f1b::e14d:3d69
- DFE08::280e:611:a1f4f:3d69
How the community answered
(44 responses)- A89% (39)
- B2% (1)
- C2% (1)
- D7% (3)
Why each option
IPv6 link-local addresses are identified by the FE80::/10 prefix (range FE80:: to FEBF::) and are used exclusively for communication on a single network segment.
FE80::380e:611a:e14f:3d69 begins with FE80, placing it within the FE80::/10 link-local prefix range defined by RFC 4291. Link-local addresses are automatically configured on every IPv6-enabled interface and are valid only for local-link communication.
Although FE80::280:512b:e14f:3d69 starts with FE80, the interface identifier 0280:512b:e14f:3d69 does not conform to the EUI-64 modified format; the universal/local bit in the first octet is not set as expected for a standard MAC-derived link-local address.
FEFE:0345:5f1b::e14d:3d69 begins with FEFE, which falls outside the FE80::/10 link-local prefix range and is therefore not a valid link-local address.
FE08::280e:611:a1f4f:3d69 begins with FE08 rather than FE80 (digits are transposed), and the group 'a1f4f' contains five hexadecimal digits, which is invalid in IPv6 notation.
Concept tested: IPv6 link-local address prefix identification FE80::/10
Source: https://www.rfc-editor.org/rfc/rfc4291#section-2.5.6
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