IPv6 global unicast addresses — scope and routability Which statement correctly describes an IPv6 global unicast address and how it compares to familiar IPv4 addressing?

Introduction / Context:
IPv6 replaces IPv4 public addressing with a much larger, structured global address space. Global unicast addresses (GUA) provide globally routable identifiers for hosts and routers, enabling end-to-end connectivity without the pervasive network address translation typical of IPv4 deployments.

Given Data / Assumptions:

• Global unicast addresses commonly fall under 2000::/3.
• We consider default Internet routing policies that accept and propagate GUAs.
• No special constraints such as uRPF failures or route filtering beyond normal practices are assumed.

Concept / Approach:
Global unicast addresses are the IPv6 equivalent of globally routable IPv4 addresses. They are intended to be advertised via BGP on the Internet, reachable across domains, and used for server and client addressing where global reachability is required. They are distinct from unique local addresses (internal only) and link-local addresses (single-hop only).

Step-by-Step Solution:
Identify the scope: GUA provides Internet-wide routability.Contrast with ULA (internal only) and link-local (nonrouted).Select the answer that explicitly states public, global routability similar to IPv4 public addresses.

Verification / Alternative check:
Examine global BGP tables to find prefixes under 2000::/3. These are propagated and reachable across providers, demonstrating their public routability.

Why Other Options Are Wrong:

• A: True for any unicast, but does not distinguish GUA.
• C: Describes ULA semantics, not GUA.
• D/E: Describe nonrouted categories (for example, link-local) and are inconsistent with global routing.

Common Pitfalls:
Assuming all unicast in IPv6 is globally routable. Only GUA has that intended scope; ULA and link-local have more limited reach.

Final Answer:
These are your typical publicly routable addresses, comparable to globally routable IPv4 addresses.