Subnetting

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

IPv6 subnetting is the division of an IPv6 address block into smaller subnetworks by allocating bits from the subnet identifier.

IPv6 subnetting divides an IPv6 address block into smaller subnetworks by allocating bits from the subnet identifier. A typical enterprise allocation is a /48 global routing prefix, followed by a 16-bit subnet identifier and a 64-bit interface identifier. section 20.5.1

The process follows the same principle as IPv4 subnetting: extending the prefix divides the available address block into smaller networks. For a /48 IPv6 block normally used with /64 subnets, the subnet identifier supplies the values that distinguish each subnet. section 20.5.1 section 11.1

Subnetting 2001:db8:8b00::/48

Using the 16-bit subnet identifier produces /64 subnets such as 2001:db8:8b00::/64 with identifier 0x0000, 2001:db8:8b00:1::/64 with identifier 0x0001, and 2001:db8:8b00:2::/64 with identifier 0x0002. 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 locate the global routing prefix, subnet identifier, and interface identifier within an IPv6 global unicast address. section 20.5.1

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

How deep it goes

Defines the /48, /64, subnet-identifier, and interface-identifier relationship, then demonstrates several subnet values without deeper configuration detail.

Examples

Demonstrates 2001:db8:8b00::/48 divided into /64 subnets using subnet identifiers 0x0000, 0x0001, and 0x0002.

What it assumes

Assumes familiarity with IPv4 subnetting while defining the IPv6 global routing prefix, subnet identifier, and interface identifier.

What you can do after

Apply it to identify IPv6 subnet boundaries and enumerate /64 subnet addresses within a /48 allocation.

How it connects

Connects global routing prefixes with subnet identifiers, interface identifiers, IPv6 global unicast addresses, and IPv4 subnetting.

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Also explained in

• 

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  Terraform in Depth: Infrastructure as Code with Terraform and OpenTofuSubnetting is the process of dividing an IP network into smaller networks by extending its network prefix.

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Related concepts

• subnetworkproduces · A subnetwork is a logical subdivision of an IP network with its own address range, routing scope, and network configuration.
• variable-length subnet maskingincludes · Variable-length subnet masking is a subnetting method that divides an address block into subnets of different sizes based on address requirements.
• fixed-length subnet maskingincludes · Fixed-length subnet masking is a subnetting technique that divides an address space into subnets of the same size.
• network segmentationkind of · Network segmentation is the division of a network into distinct physical or logical zones with controlled communication between them.
• borrowed bitused by · A borrowed bit is a host bit reassigned to the network portion of an IPv4 address during subnetting.

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.