This post begins a series that will create a sample IPv6 address plan for a medium sized company with multiple office sites and multiple hosting locations.
In prior posts, I’ve written about IPv6 address plans in general and shown an especially interesting plan from UCSD.EDU. This post begins to “do the math” for a hypothetical company to produce a concrete addressing plan. This company is similar to my employer but I’ve thrown in a few things that we don’t have that many other more typical companies will have.
For the purpose of this thought experiment, we’ll use a company that looks like this:
- six office locations (cities)
- three co-location facilities that host consumer-facing services
- is part of a larger multi-national, but there is no higher-level single global network
For the office locations we’ll use these criteria:
- around 5000 employees total
- some locations have multiple large groups
- most users have at least four devices that need an IP address, many have six and some have 10
- two of the locations have their own Internet connections as well as a connection on the internal WAN
- some locations have multiple Internet connections from multiple providers
The co-location facilities look like this:
- up to 5000 hosts (or instances) per location
- multiple Internet connections from multiple providers
- each location houses sub-facilities that are leased to other business units (separate private clouds and the like)
- each sub-facility needs to be independently routable via separate ISPs (not all use the same ISPs)
- also used for Disaster Recovery (DR) for the offices
With this information, we can begin to create the IPv6 address plan. Creating the plan begins with determining the Assigned Global Routing Prefix and subnet sizes and concludes with subnet numbering and routing plans.
The constraints we have to work within are:
- The assignment of the Global Routing Prefix is gone by an Internet Registrar according to their policies. You must justify the size of the allocation you request.
- Subnets are “always” on a /64 boundary (host identifiers are “always” 64 bits)
- “Sites” are groups of subnets on a /48 boundary
- Only networks with prefixes at /48 or larger are considered “publicly routable” by most ISPs. They won’t announce routing data for anything smaller.
Next time, I’ll look at these constraints and how they factor into the size of a desired Global Routing Prefix and creating a site and subnet plan.