Provider aggregatable address space
Provider Aggregatable Address Space (PA address space) are Internet protocol addresses that are allocated (allocated) by a Regional Internet Registry (RIR) to a Local Internet Registry (LIR), which divides them into smaller networks (sub-allocated) and to their customers (assigned).
Usually z. B. a smaller Internet service provider connection (upstream) to other subscriber networks with a larger one (usually a LIR) and receives from this in justified cases also PA IP addresses if he does not have his own PI addresses . This leads to difficulties if the smaller provider uses several Internet connections or wants to change its upstream provider , since the IP addresses remain with the LIR and have to be returned.