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Enterprise IPv6 address planning considerations

By Paul Zawacki, senior principal network engineer at Oracle, special to Network World
January 25, 2011 05:51 PM ET

Network World - With interest in IPv6 accelerating and adoption heating up more attention is being paid to address planning, but where do you start?

Organizations should already be working toward securing an adequately sized address block. You want to move quickly to avoid the possibility of demand exceeding the capacity of Regional Internet Registries and Service Provider's ability to service these requests quickly. If it turns into a land grab as some predict, you want to be ahead of the pack.

Provider Independent (PI) public ranges are attractive for internal enterprise deployments to avoid the complexities of overlapping private network ranges, something all too common in IPv4 with mergers and acquisitions. Advertising IPv6 routes externally on the Internet may require a different addressing strategy. But how do you know how much addressing you need and how do you begin creating an address plan? This article suggests some considerations for global unicast address planning internal to the enterprise.

QUIZ: How prepared are you for IPv6?

There is a great deal of custom design and sizing work in IPv4, consuming organizational resources that could best be used elsewhere. Sizing work often includes defining major blocks for geographic regions or services and applications, identifying site or service boundaries, and provisioning networks.

If you guess wrong, you might have a painful and expensive readdressing exercise in your future. As a consequence, network designers sometimes guess high to avoid these concerns but this leads to wasted space. If you guess too low it may lead to fragmentation and limit route aggregation potential. In IPv4 it is a balancing act with space conservation being a top priority. Many of these barriers are lifted in IPv6, assuming of course you are successful in acquiring an adequately sized address block for your organization. Size does matter.

Your IPv6 migration project hopefully begins with a structured engineering approach and documented requirements. A priority at this stage is to reduce or eliminate the need for time-consuming custom design work. Think in terms of standardization, from the regional blocks and services or applications, to site sizes, how sites are allocated, and even how to address hosts within each network.

Standardization may be viable at every level, something simply not possible for large organizations in IPv4. The result not only reduces engineering efforts and the burden of registrations and management, but can also open new opportunities for replication and automation while facilitating provisioning in dense virtual environments. Standardize, automate, provision.

Standardization of geographic regional blocks, services, or applications results from decisions about site size, the number of sites required, and space reserved for future requirements. Site sizes may be standardized assuming some tolerance for wasted space. Again, while space conservation is a prime concern in IPv4, the balance in IPv6 may tip toward new opportunities at the expense of some acceptable level of waste.

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