A communication network is described that allows legacy devices to access an IMS network. The communication network includes a switching system, an IMS network, and a non-IMS network. The switching system includes a subscriber database that is pre-provisioned with identities of IMS subscribers using legacy devices. When in operation, a calling party places a call through a legacy device. The switching system receives the call and accesses the subscriber database based on a calling party identifier (e.g., a phone number, URL, etc) to determine if the calling party is an IMS subscriber. If the calling party is an IMS subscriber, then the switching system routes the call to the IMS network. If the calling party is not an IMS subscriber, then the switching system routes the call to the non-IMS network.