Location Routing Number LRN

NANP

A ten-digit number that identifies the switch serving a ported number, so calls route to the right network.

A Location Routing Number (LRN) is a ten-digit number that uniquely identifies the local switch (or point of interconnection) currently serving a telephone number. When a number is ported, the network performs an LRN "dip" to find where to route the call, rather than relying on the number's original NXX assignment.

The LRN is why calls to a ported number still reach the correct carrier even though the number's NXX was assigned to a different provider.

Carrier names are illustrative. The lesson is real: the assignment record (who a prefix was handed to) is not the current carrier (who serves a number now). After a port they differ — which is why an area code, or an old assignment table, cannot tell you who a number belongs to today.

Common misconception.

The LRN is not the subscriber's phone number and is not visible to callers. It is routing infrastructure that resolves who serves a number after portability.