What is local number portability?
Local Number Portability (LNP) is a service provided by a telecommunications service provider that enables users to transfer their telephone number between different service providers and geographic locations. It allows users to keep the same landline or telephone number while switching their local exchange service (LEC).
LNP primarily helps telecom end users access the existing number regardless of their physical location or the service provider used. For example, through LNP, a local resident can carry / port an existing number even if it has moved to a new provider, new home, or even a new city.
Typically, LNP operates through a Local Routing Number (LRN) service, which provides a call forwarding service to telecommunications operators. In the US, the LNP and LRN are managed by Number Portability Management Centers (NPAC) which each time a customer switches between providers, they generate a new LRN and send that LRN to the new provider to route calls for that number.