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200-150 · Question #50

Which two statements describe characteristics of IPv6 unicast addressing? (Choose two.)

The correct answer is A. Global addresses start with 2000::/3. D. There is only one loopback address and it is ::1. IPv6 global unicast addresses are allocated from the 2000::/3 block, and the only loopback address in IPv6 is the single address ::1.

Cisco Data Center Networking Technologies

Question

Which two statements describe characteristics of IPv6 unicast addressing? (Choose two.)

Options

  • AGlobal addresses start with 2000::/3.
  • BLink-local addresses start with FE00:/12.
  • CLink-local addresses start with FF00::/10.
  • DThere is only one loopback address and it is ::1.
  • EIf a global address is assigned to an interface, then that is the only allowable address for the

How the community answered

(40 responses)
  • A
    85% (34)
  • B
    3% (1)
  • C
    10% (4)
  • E
    3% (1)

Why each option

IPv6 global unicast addresses are allocated from the 2000::/3 block, and the only loopback address in IPv6 is the single address ::1.

AGlobal addresses start with 2000::/3.Correct

Global unicast addresses begin with the binary prefix 001, meaning the range spans from 2000:: through 3FFF:FFFF:...:FFFF, expressed as the prefix 2000::/3, and these are the publicly routable IPv6 addresses assigned by IANA.

BLink-local addresses start with FE00:/12.

Link-local addresses start with FE80::/10 (binary 1111 1110 10), not FE00:/12 - FE00:/12 would encompass a broader range that includes reserved addresses.

CLink-local addresses start with FF00::/10.

FF00::/10 is the prefix for IPv6 multicast addresses, not link-local addresses - confusing multicast and link-local is a common error.

DThere is only one loopback address and it is ::1.Correct

IPv6 defines exactly one loopback address, ::1 (the 128-bit address with all zeros except the final bit), equivalent to 127.0.0.1 in IPv4, and no other loopback addresses exist in IPv6.

EIf a global address is assigned to an interface, then that is the only allowable address for the

An IPv6 interface can have multiple addresses simultaneously, including a link-local address, one or more global unicast addresses, and a loopback address.

Concept tested: IPv6 unicast address types and prefixes

Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6_basic/configuration/xe-16/ip6b-xe-16-book/ip6-add-basic-conn.html

Topics

#IPv6 unicast#global address#link-local#loopback

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