Any IP telephone (also referred to as a User Agent in the SIP world) that conforms to accepted SIP standards can interoperate with the sipXecs system. There are literally hundreds of hardware and software-based phones that will work. If there is any question whether a device will work with the system, SIPfoundry offers an automated interoperability testing server (http://interop.pingtel.com).
When most hardware-based phones boot, they can check a configuration server for a configuration file. The configuration file is generally transferred by the phone with TFTP, FTP, or HTTP. The configuration file format varies for each phone vendor but typically the configuration file will have the MAC address (Media Access Control address, or more commonly known as the Ethernet hardware address, which is unique to every Ethernet device) of the phone in its name.
The sipXecs system knows how to generate configuration files for many different types...