What is PI address space?

PI (Provider Independent) address space is an IP resource assigned directly to an end user, independent of any connectivity provider. The same addresses can be announced in BGP through any operator and kept when you change providers. Its opposite is PA (Provider Aggregatable) space: addresses carved out of one operator's larger allocation that are tied to that operator's network and must be returned when you leave. The PI vs PA distinction determines address portability and whether a network can genuinely multihome.

PI vs PA: the core difference

PA addresses come from an operator's (LIR's) pool and form part of its aggregate, so they scale well in the global routing table but are non-portable: a customer uses them only while connected to that operator. PI addresses are assigned by a RIR (in our region RIPE NCC, under the Internet Numbers Registry System described in RFC 7020) directly to an end organisation, usually via an LIR, and are not tied to any link. That makes them portable, but every PI prefix must be announced on its own, which adds entries to the global table.

• PA: addresses from a provider's aggregate, non-portable, returned on provider change.
• PI: addresses assigned directly to an organisation, portable between providers.
• Smallest announceable prefix is a /24 for IPv4 and typically a /48 for IPv6.
• PI does not aggregate into a provider's network, so each prefix is a separate table entry.
• Announcing PI in BGP requires your own ASN plus matching IRR objects and a ROA (RPKI).

Portability and multihoming

The main advantage of PI space is provider independence. PA addresses can only be announced through the operator they came from, so a network built solely on PA is locked to one upstream and faces renumbering on every change. PI space solves both problems: the same prefixes can be announced in parallel to several operators. That is the prerequisite for true multihoming and for resilience against a single provider's outage. Changing operators no longer means renumbering the whole infrastructure, which is a large saving across many servers and firewall rules.

Cost and obligations of holding PI

Portability has a price. A PI prefix does not aggregate into a provider's network, so each block adds an entry to the global routing table, which is why RIRs gate assignments with policy and fees. A PI holder is responsible for correct route objects in the IRR, for publishing a ROA in RPKI (to enable route origin validation) and for compliance with the minimum prefix-length filters (/24 in IPv4, /48 in IPv6) that operators apply. Without these, a PI prefix is filtered out and stays unreachable despite a valid assignment.

PI space on the AS202520 SkyPass network

AS202520 SkyPass announces customer PI prefixes over IP transit and peering at Polish internet exchanges (THINX, TPIX, WRIX, 1-IX) from PoPs in Warsaw and Wroclaw. We help configure the BGP session, verify IRR objects and RPKI ROAs, and tune your announcement policy so your PI block is correctly visible and portable independently of your other providers. You can then multihome on your own address space and treat our upstream as one of several independent paths to the internet.