Provider-independent IP addresses: PI versus PA

Provider-independent (PI) address space is registered independently of any single upstream Internet provider. A holder can normally retain it when changing providers, subject to registry policy and routing arrangements. PI does not automatically make a service reachable worldwide: network operators must accept and carry the route to the prefix.

The difference between PI and PA

Provider-aggregatable (PA) space comes from an operator’s allocation and is assigned to customers. If a customer changes providers, it will usually renumber services into the new provider’s addresses. PI space is registered separately to its holder and can be announced through more than one provider. An organisation may need its own ASN and BGP configuration for this design, depending on the agreements with its operators. PI provides addressing independence, not independence from Internet connections or sound network administration.

Current availability in the RIPE NCC region

RIPE NCC does not issue new IPv4 PI assignments because the available IPv4 pool for them has run out. Existing assignments may continue under the rules; transfers and other cases have their own processes. IPv6 PI remains available when the applicant meets the applicable conditions. The RIPE NCC explanation of PA and PI states the current distinction and availability. Do not confuse a new IPv4 PI assignment with an IPv4 allocation from a waiting list or a transfer of existing resources.

A two-provider example

A company announces a PI prefix through two providers with an agreed ASN. If one connection fails, traffic may continue over the other if routes are correctly announced and accepted. BGP does not promise instantaneous failover, and different parts of the Internet can temporarily see different paths. The company needs agreements about announcements, accurate route registration, filters and a controlled failure test. Some operators may filter prefixes that do not meet their routing policy; a very small block is not guaranteed universal reachability.

When PI is worth the effort

PI can reduce the number of addresses that must change during an ISP migration, but it adds work: route management, monitoring, registry records and coordination with operators. A small network may find it simpler to use the new provider’s PA addresses and plan DNS and service changes in advance. PI is registered to a resource holder, not an employee as a “personal IP”. It does not replace firewalls, server security or capacity planning. Before acquiring existing IPv4 space, check its registration history and the registry’s transfer procedure.