IPv6 addressing fundamentals — identifying a unicast address behaviour In Internet Protocol version 6 (IPv6) networking, which statement correctly describes the delivery semantics of a unicast address (that is, any IPv6 address type that represents a single destination interface rather than a group or anycast)?

Introduction / Context:
Understanding the basic categories of Internet Protocol version 6 (IPv6) addresses is crucial for network design and troubleshooting. IPv6 defines several address types, including unicast, anycast, and multicast. This question focuses on what makes a unicast address unique: it represents a single destination interface so that traffic is delivered to exactly one endpoint in normal operation.

Given Data / Assumptions:

• We are comparing IPv6 address categories conceptually.
• We assume standard behaviour without special features such as anycast configured on identical addresses across multiple nodes.
• No tunnelling, NAT64, or traffic engineering tricks are assumed.

Concept / Approach:
In IPv6, a unicast address identifies a single interface. A packet sent to a unicast destination is forwarded by routers along the best path and ultimately delivered to the one interface that owns that address. This is different from multicast (one to many) and different from anycast (one to nearest of many, where the same address is configured on multiple interfaces and routing selects the closest). Global unicast, unique local, and link-local are all subtypes of unicast; they differ by scope and routability, not by the fundamental “one destination interface” delivery model.

Step-by-Step Solution:
Identify the core definition: unicast means one-to-one delivery.Differentiate from multicast (one-to-many) and anycast (one-to-nearest-of-many).Recognize that global unicast, unique local, and link-local are all still unicast subtypes and therefore follow one-to-one delivery semantics.Select the statement that reflects one-to-one delivery to a single interface.

Verification / Alternative check:
Check any standard IPv6 reference: unicast traffic has a single intended receiver, multicast traffic is replicated to group members, and anycast traffic is delivered to the nearest node advertising the shared anycast address.

Why Other Options Are Wrong:

• B: Describes global unicast specifically, not unicast as a general behaviour, and is incomplete.
• C: Describes unique local addresses by analogy to IPv4 private space, not unicast as a whole.
• D: Describes link-local addresses being nonroutable and nearly unique; still not the defining unicast behaviour.
• E: Replication to multiple receivers is multicast, not unicast.

Common Pitfalls:
Confusing unicast as a subtype instead of a category. Recall that global unicast, unique local, and link-local are all unicast, but the essential characteristic is single-interface delivery.

Final Answer:
Packets addressed to a unicast address are delivered to a single interface.