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hardmultiple choiceObjective-mapped

Which IPv6 prefix is used for link-local addresses?

Answer choices

Why each option matters

Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.

A

Distractor review

FC00::/7

FC00::/7 is unique local addressing, not link-local.

B

Best answer

FE80::/10

Correct. FE80::/10 is the link-local prefix.

C

Distractor review

2000::/3

2000::/3 is global unicast space.

D

Distractor review

FF00::/8

FF00::/8 is multicast space.

Common exam trap

Common exam trap: answer the scenario, not the keyword

A frequent exam trap is selecting FC00::/7 as the link-local prefix because it resembles private addressing similar to IPv4’s private ranges. However, FC00::/7 is actually the unique local address space, which is routable within an organization but not globally. Another common mistake is confusing FE80::/10 with global unicast addresses like 2000::/3, which are routable on the internet. This confusion arises because both address types start with 'F' and are IPv6 prefixes. Candidates must remember that link-local addresses are always FE80::/10 and are only valid on the local link, used for essential functions like neighbor discovery and routing adjacency formation.

Technical deep dive

How to think about this question

IPv6 link-local addresses are a fundamental part of IPv6 networking, used for communication within a single local network segment or link. These addresses are automatically configured on all IPv6-enabled interfaces and do not require manual configuration or DHCP. The link-local prefix FE80::/10 designates these addresses, which are essential for network functions such as neighbor discovery, address autoconfiguration, and routing protocol operations within the local link. They are not routable beyond the local network segment, ensuring that traffic using link-local addresses remains confined to the local link. The IPv6 standard defines FE80::/10 as the reserved prefix for link-local addresses, meaning the first 10 bits of the address are fixed as 1111 1110 10. This prefix is followed by 54 bits set to zero, and the remaining 64 bits are typically derived from the interface identifier, often based on the MAC address or generated randomly for privacy. Cisco devices use these addresses for critical internal processes, including OSPFv3 adjacency formation and routing updates, which rely on link-local communication to establish neighbor relationships without requiring global or unique local addresses. A common exam trap is confusing link-local addresses with unique local addresses (FC00::/7) or global unicast addresses (2000::/3). While unique local addresses resemble private IPv4 addresses and are routable within an organization, link-local addresses are strictly local and cannot be routed. Understanding this distinction is crucial for CCNA candidates, as misidentifying the prefix can lead to incorrect answers. Practically, Cisco routers use link-local addresses for routing protocol neighbor discovery, making FE80::/10 indispensable in IPv6 network operations.

KKey Concepts to Remember

  • IPv6 link-local addresses use the FE80::/10 prefix and are automatically assigned to all IPv6-enabled interfaces for local link communication.
  • Link-local addresses are not routable beyond the local network segment and are essential for neighbor discovery and routing protocol adjacency formation.
  • The FE80::/10 prefix consists of a fixed 10-bit pattern followed by 54 bits set to zero and a 64-bit interface identifier.
  • Unique local addresses use the FC00::/7 prefix and are routable within an organization but not on the global internet.
  • Global unicast addresses use the 2000::/3 prefix and are routable on the internet, unlike link-local addresses.
  • Multicast addresses use the FF00::/8 prefix and serve different purposes unrelated to link-local communication.
  • Cisco routing protocols like OSPFv3 rely on link-local addresses for establishing neighbor relationships and exchanging routing information.
  • IPv6 link-local addresses enable essential network functions without requiring manual configuration or DHCP.

TExam Day Tips

  • Watch for words such as best, first, most likely and least administrative effort.
  • Review why wrong options are wrong, not only why the correct option is correct.

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More questions from this exam

Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.

Question 1

A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?

Question 2

A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?

Question 3

What is the OSPF metric called?

Question 4

A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?

Question 5

A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?

Question 6

A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?

FAQ

Questions learners often ask

What does this 200-301 question test?

IPv6 link-local addresses use the FE80::/10 prefix and are automatically assigned to all IPv6-enabled interfaces for local link communication.

What is the correct answer to this question?

The correct answer is: FE80::/10 — IPv6 link-local addresses come from FE80::/10. They are valid only on the local link and are commonly used for neighbor discovery and routing adjacency formation.

What should I do if I get this 200-301 question wrong?

Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.

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