Understanding IPv6 link-local addresses: Which statement correctly describes IPv6 link-local addresses and their routing characteristics?

Introduction / Context:
Every IPv6 interface automatically configures a link-local address (fe80::/10). These addresses are essential for neighbor discovery and local communications, but they have strict scope and routing rules compared to global unicast addresses.

Given Data / Assumptions:

• Link-local scope is a single Layer 2 segment (link).
• Routers must not forward link-local packets between links.
• Examples: router neighbor adjacencies, SLAAC operations.

Concept / Approach:

Link-local addresses are nonroutable beyond the local link. They are somewhat analogous in spirit to RFC1918 private IPv4 addresses with respect to nonroutability, though their purpose and scope are different. Global communication uses global unicast addresses (2000::/3).

Step-by-Step Solution:

Verification / Alternative check:

Attempting to route to a link-local address via a router fails across subnets; packet captures show link-local traffic limited to the local segment. Routing tables will not contain routes to foreign link-local networks.

Why Other Options Are Wrong:

(A) is a generic unicast statement and does not address scope.

(B) incorrectly claims link-local are publicly routable.

(D) better fits unique-local (fc00::/7) characteristics but still not precise for link-local scope and use.

Common Pitfalls:

Trying to ping a remote device’s link-local address without specifying an outgoing interface; assuming link-local can traverse routers; mixing up link-local with unique-local (ULA).

Final Answer:

These are like private addresses in IPv4 in that they are not meant to be routed.