Cisco Certified Network Associate (CCNA) Practice Exam

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Which of the following is NOT a component of an IPv6 header?

Version
Flow label
Time-to-live
Hop limit

The correct answer is: Time-to-live

The correct choice is based on the structure of an IPv6 header. In IPv6, the header includes several key fields designed to facilitate routing and delivery of packets through a network. The fields include the Version, which identifies the IP version being used, and the Flow Label, which provides special handling for packets belonging to a specific flow or session. The Hop Limit field serves a similar purpose to what is known as Time-to-Live (TTL) in IPv4. However, since the question specifically asks for a component that does not exist in an IPv6 header, the Time-to-Live term is not used in IPv6; instead, the equivalent functionality is represented by the Hop Limit. This distinction is important because it reflects the changes made in the transition from IPv4 to IPv6, with an emphasis on new header fields and the streamlining of existing functions. Thus, in the context of IPv6 headers, Time-to-Live is not a relevant component.