Global unicast address

As explained in Acing the CCNA Exam: Volume 1 Fundamentals and Protocols

A global unicast address is an IPv6 unicast address that is globally unique and routable over the internet.

A global unicast address is an IPv6 address that is globally unique and routable over the public internet. Enterprises normally receive an address block from an ISP or regional internet registry rather than choosing one freely. section 20.5.1

A typical global unicast address is organized into three parts:

• A 48-bit global routing prefix assigned by an ISP or regional internet registry. section 20.5.1
• A 16-bit subnet identifier used to create separate /64 subnets. section 20.5.1
• A 64-bit interface identifier representing the host portion of the address. section 20.5.1

Example /48 allocation

Given 2001:db8:8b00::/48, an enterprise can create subnets such as 2001:db8:8b00::/64, 2001:db8:8b00:1::/64, and 2001:db8:8b00:2::/64. The 2001:db8::/32 range is reserved for documentation examples. section 20.5.1

Figure 20.7 The structure of an IPv6 global unicast address. The first 48 bits are the global routing prefix, assigned to the enterprise by the ISP. The next 16 bits are the subnet identifier, which the enterprise can use to make various subnets. The remaining 64 bits are the interface identifier—the host portion of the address.

Use the address-structure diagram to distinguish the global routing prefix, subnet identifier, and interface identifier. section 20.5.1

How Acing the CCNA Exam: Volume 1 Fundamentals and Protocols covers it

How deep it goes

Explains allocation, address structure, /64 subnetting, and the historical 2000::/3 range without detailing routing protocols.

Examples

Uses the 2001:db8:8b00::/48 block to demonstrate successive /64 subnets.

What you can do after

Apply the three-part structure to identify prefixes, subnet identifiers, and host portions in IPv6 addresses.

How it connects

Connects IPv6 subnetting, interface identifiers, public IPv4 addresses, ISPs, and regional internet registries.

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Related concepts

• public ip addressequivalent to · A public IPv4 address is a globally unique IPv4 network address routable on the public Internet and assigned to an internet-facing resource.
• interface identifierhas part · An interface identifier is the portion of an IPv6 address that identifies a specific network interface within its address prefix.
• IPv6kind of · IPv6 is the sixth version of the Internet Protocol, using 128-bit network addresses for packet-based communication.

This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 1 Fundamentals and Protocols. The section links point to the parts of the book it draws on.