Routing methods and systems using ENUM servers internal and external to a service provider network

A Voice over Internet Protocol (VoIP) call from a first provider to a destination telephone number served by a second provider comprises sending a Session Initiation Protocol (SIP) INVITE message from an originating switch to a first SIP server of the first provider. The first SIP server queries a telephone number mapping (ENUM) server of either the first, second or a third provider, and receives a Uniform Resource Identifier (URI) associated with the destination telephone number. The ENUM server may be internal or external to the first provider. The first provider queries a Domain Name Service (DNS) server based on the URI, and receives an Internet Protocol (IP) address of a second SIP server of the second provider. The first SIP server and the second SIP server are used to set up a bearer path for the VoIP call between the originating switch and a destination switch.