These pages and the links below are presented in the format of ARIN policy that was effective through October 14, 2004. This method of formatting was superseded by the format in the Number Resource Policy Manual (NRPM), which was published on October 15, 2004.
ARIN has adopted the reassignment guidelines recommended by the IAB/IESG pending future review based on operational experience. Those guidelines are as follows:
The IESG and the IAB recommend the allocations for the boundary between the public and the private topology to follow those general rules:
- /48 in the general case, except for very large subscribers.
- /64 when it is known that one and only one subnet is needed by design.
- /128 when it is absolutely known that one and only one device is connecting.
In particular, we recommend:
- Home network subscribers, connecting through on-demand or always-on connections should receive a /48.
- Small and large enterprises should receive a /48.
- Very large subscribers could receive a /47 or slightly shorter prefix, or multiple /48's.
- Mobile networks, such as vehicles or mobile phones with an additional network interface (such as bluetooth or 802.11b) should receive a static /64 prefix to allow the connection of multiple devices through one subnet.
- A single PC, with no additional need to subnet, dialing-up from a hotel room may receive its /128 IPv6 address for a PPP style connection as part of a /64 prefix.
Note that there seems to be little benefit in not giving a /48 if future growth is anticipated.
The above IAB/IESG recommendations are described in more detail in RFC 3177