Cisco CEoIP network modules provide a virtual circuit through an IP network (similar to a leased line). Transport of data, regardless of the content or structure of the data stream, is entirely transparent to the destination; bits arriving at one end are delivered unchanged to the destination address. The 4-port T1/E1 RJ-48 interface network module (NM-CEM-4TE1) is a single-width CEoIP network module with four T1/E1 ports. The NM-CEM-4TE1 connects to any T1/E1 interface for voice or data.