Planning Address Allocation (IPv6)

The Internet Assigned Numbers Authority (IANA) oversees global IP address allocation. IANA delegates allocations of IP address blocks to Regional Internet Registries (RIR). Each RIR represents a geographical area. Some examples of RIRs are as follows:

■ ARIN: American IPv6 Registration Services (

■ APNIC: Asia Pacific Network Information Center

■ RIPE: European Regional Internet Registry (

RIRs allocate IPv6 addresses for local ISPs and end users. Most ISPs follow their RIR’s guidelines to allocate single /48 subnets. A typical /48 allocation gives an enterprise 65,536/64 networks. Each /64 subnet has 264 IPv6 addresses.

On receiving an IPv6 subnet, organize the address-space assignments further into enterprise-local subnets for efficient routing and aggregation. The best practices of planning IPv6 addresses are debatable. However, the following standard guidelines exist:

■ Ensure that every LAN subnet is a /64 network. A good starting point would be to count the VLANs and anticipate how many networks would be needed in the future.

■ Determine the address space needed for network identifiers. For example, a /56 xxx would provide 256/64 networks and a /52 xxx would provide 4096/64 networks. The 4-bit separation is for easier readability; however, any bit in between can be used.

■ Use /126 networks in the zero address space for link networks (router to router).

This is also recommended in RFC 3627.


In this topic, IPv6 deployment planning was discussed. The starting points show how the IPv6 deployment process can be started. This includes planning, building a business case, and building a team to oversee the IPv6 deployment.

A trial of IPv6 should be done in a lab environment to gain familiarity with the technology and prepare for a pilot on the live network.

IPv6 address allocation and how to obtain an IPv6 address were discussed toward the end, along with some guidelines that can be used for planning an IPv6 addressing scheme.

Next post:

Previous post: