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GCIA · Question #18

What is the order of the extension headers that is followed by IPv6?

The correct answer is D. IPv6 header, Hop-by-Hop, Destination Options (first), Routing, Fragment, Authentication, Encrypted. RFC 8200 defines a recommended order for IPv6 extension headers, beginning with the IPv6 header and Hop-by-Hop Options and ending with ESP before the upper-layer protocol.

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Question

What is the order of the extension headers that is followed by IPv6?

Options

  • ADestination Options (first), Routing, IPv6 header, Hop-by-Hop, Fragment, Authentication, Encrypted
  • BRouting, Hop-by-Hop, Destination Options (first), Fragment, Authentication, Encrypted Security Payload,
  • CFragment, Routing, Hop-by-Hop, Destination Options (first), Authentication, Encrypted Security Payload,
  • DIPv6 header, Hop-by-Hop, Destination Options (first), Routing, Fragment, Authentication, Encrypted

How the community answered

(32 responses)
  • A
    3% (1)
  • B
    16% (5)
  • C
    9% (3)
  • D
    72% (23)

Why each option

RFC 8200 defines a recommended order for IPv6 extension headers, beginning with the IPv6 header and Hop-by-Hop Options and ending with ESP before the upper-layer protocol.

ADestination Options (first), Routing, IPv6 header, Hop-by-Hop, Fragment, Authentication, Encrypted

This order is incorrect because the IPv6 header must always appear first, and Destination Options cannot precede Hop-by-Hop Options or the Routing header in the recommended sequence.

BRouting, Hop-by-Hop, Destination Options (first), Fragment, Authentication, Encrypted Security Payload,

This order is incorrect because the Hop-by-Hop Options header must immediately follow the IPv6 header and cannot appear after Routing and Destination Options headers.

CFragment, Routing, Hop-by-Hop, Destination Options (first), Authentication, Encrypted Security Payload,

This order is incorrect because the Fragment header cannot appear before Hop-by-Hop Options; RFC 8200 requires Hop-by-Hop Options to immediately follow the IPv6 header.

DIPv6 header, Hop-by-Hop, Destination Options (first), Routing, Fragment, Authentication, EncryptedCorrect

RFC 8200 specifies the recommended extension header order as IPv6 header, Hop-by-Hop Options, Destination Options (first destination), Routing, Fragment, Authentication Header, Encapsulating Security Payload, and then the upper-layer header - this sequence matches choice D exactly.

Concept tested: IPv6 extension header ordering per RFC 8200

Source: https://www.rfc-editor.org/rfc/rfc8200

Topics

#IPv6#extension headers#packet structure#header ordering

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