The Site Local Address

A site is an organization or part of an organization. It could be a certain topological location, or it could be multiple topological locations interconnected in some way. A network configured with a site-local address is not reachable from locations outside the site. The site's edge routers must be able to keep site-local traffic within the site and are responsible for controlling the route propagation. In addition to the site-local FP and Interface ID, site-local addresses have a subnet identification field. Note, however, that no TLA or NLA IDs exist. These addresses are designed to be used within a site only; no global prefix is required. Use of these addresses is identical to the private IPv4 addresses. The addresses are not globally unique. It is recommended that you use site-local addresses, not global aggregatable addresses, on router interfaces.

The site-local address is defined by FP 1111111011 and is followed by 38 zeros, a 16-bit subnet field, and the 64-bit Interface ID, as illustrated in Figure 8-6.