Monday, May 6, 2013

IPv6 Address Planning

If you are putting together your IPv6 address plan, you'll need to consider how you should allocate subnets from the IPv6 block you received from your ISP or Internet Registry. In fact you should consider how to design the structure of your IPv6 allocation hierarchy to simplify ongoing network management once deployment has begun. 

The first step entails defining how much address space is required across and into the depths of your IP network to provide IPv6 address capacity for those devices requiring it. You can use your current IPv4 address allocation record as a guide to define the active utilization of your IPv4 address space. Once you've defined where you require IPv6 addresses, you'll next need to define how to perform your allocations. One approach is to simply allocate /64 subnets directly from your base ISP allocation, using a sparse, best-fit or random allocation approach. 

This single-tier allocation approach may work fine for small networks, but for modest to larger networks, mapping your allocations to network topology (and other factors we'll consider next) can simplify routing and ongoing management of your network. For example, if you operate a traditional core-access-local network architecture, you may consider allocating large allocations from your ISP allocation to your core components or routers. Subtending access components or routers can then be allocated blocks that "roll-up" or are allocated from their respective core components. Likewise local networks and subnets can be allocated from respective access components. This approach renders a hierarchical aggregation model that streamlines route advertisements within your network as routers need only communicate summarized (rolled-up) address space and not individual sub-allocations. 

However you may also want to consider inserting additional hierarchical layers to facilitate network management and security processes that are based on IP address assignments. If your network supports multiple classes of service, e.g., voice, video, and data, you may configure your routers to inspect source/destination IP addresses in the IP header to apply corresponding packet treatment. Imposing such a policy within a purely topological allocation scheme can be cumbersome. However if your first allocation tier is for class of service, followed by core, access and local tiers, the application of a class of service policy is a single router entry in every router in your network! To learn more about various IPv6 address allocation strategies, tune into our upcoming webinar which will discuss IPv6 allocation considerations including some examples and resulting network management implications. After May 8, you can access the replay from the webinars section of our IPv6 Resource Center.