IP Address Scopes

In network terminology, scope refers to the part of your network (and any interconnected networks) within which a given address is valid. IPv4 has only limited support for scopes. Address scopes are much more fully developed in IPv6. This is one of the big differences from IPv4, and is a critical part of an IPv4 engineer’s learning curve.

Typical unicast scopes are interface local (within your network interface), link local (within your subnet), site local (within a group of connected LANS that belong to your organization) and global (the entire Internet). With multicast, there are additional scopes defined, such as organization local and admin local. Unfortunately, the definition of “site” is not very well defined, so site local addresses have built in ambiguity.

IPv4 has limited support for address scopes (see IPv4 Address Scopes). The scope concept is fully developed in IPv6 (see IPv6 Address Scopes).