That is precisely why sparse allocation is preferred for service providers that need to allocate large blocks of address space to their customers. What sparse allocation provides is address space in reserve that is more likely to be contiguous.įellow routing nerds may recognize immediately that such contiguous space adjacent to the original allocation and reserved for the original allocation’s recipient, is better for enabling route summarization and reducing the size of routing tables (i.e., preventing large prefix disaggregation). The basic benefit of this method is not simply leaving space in reserve-after all, it likely wouldn’t be that hard to find available extra IPv6 address space from within the overall IPv6 allocation. The simplest description for sparse allocation of IPv6 is the assignment of prefixes with lots of additional unused prefixes (and thus address space) in between them. Since we covered the next available prefix allocation method of assigning prefixes (i.e., subnets) of IPv6 address space in detail last time, this time we’ll focus on the three allocation methods that remain.
As with our example in part one, the idea is that you’ve been allocated a sufficiently large block of IPv6 addresses to meet your IPv6 addressing needs for decades.
In part two, we’ll discuss the remaining IPv6 prefix allocation methods along with how and when to use them. If you haven’t read part one and are unfamiliar with IPv6 address planning, I encourage you to read it before reading this post. I also listed the four most common methods of IPv6 prefix allocation: next available, sparse, best fit, and random. Part one concluded with a detailed look at the next available allocation technique.
In part one, we started our discussion of IPv6 prefix allocation methods with the simple reason of why you need them in the first place: a properly sized IPv6 allocation provides a vast amount of IPv6 space and you need to have one or more methods for logically and sensibly dividing and assigning that space based on the types of networks you are addressing.
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