Unique Local Addressing Plan Example
To fully understand some of these concepts, it can be very beneficial to see how they could be used within a network. In this section an example Unique Local addressing plan will be shown. Figure 3 shows the topology for the Acme Corporation that will be used for the examples.
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Figure 3: Acme Corp – No Internet Connectivity
Acme has major operations in four U.S. cities; because each of these locations is similar in terms of the number of devices deployed, address allocation can be equal across all sites. Acme Corp also has aspirations for global expansion, and this should be considered when performing the address assignment plan as well. There is no requirement for any of these sites to have direct Internet access in this plan; assume that all sites are connected via some form of private layer 2 network.
The development of a unique local addressing plan is not all that complex because there will be well more available host addresses than what will need to be practically deployed in any modern network. There are some suggestions as to how to maintain the uniqueness of the global ID’s (locally assigned) that are used. This example follows the recommendation for locally assigned addresses as laid out in RFC 4193, which states that “Locally assigned Global IDs MUST be generated with a pseudo-random algorithm consistent with RANDOM” (RFC 4086).
Using one of the common Unique Local IPv6 global prefix generators, the Acme corporate network was assigned the global prefix of 6D8D64AF0C; when pushed together with the common unique local locally assigned prefix (FD00::/8) the prefix expands to FD6D:8D64:AF0C::/48; this leaves Acme with an additional 16 bits of space to use for subnetting across their sites. Based on this information, Acme can assign a unique subnet ID per site as shown in Table 1.
Table 1: Acme Corp - IPv6 Unique Local Address Assignment
|
Site |
IPv6 Unique Local Address Range Assignment |
|
Seattle |
FD6D:8D64:AF0C::/64 |
|
San Francisco |
FD6D:8D64:AF0C:1::/64 |
|
New York |
FD6D:8D64:AF0C:2::/64 |
|
Raleigh |
FD6D:8D64:AF0C:3::/64 |