The basic system consists of a primary router and a battery. An additional router can be added, if needed. Optional routers, radios, power supplies for crypto, servers, and switches are also available to extend the capabilities of the M3-EX system. The fanless M3-EXR and M3-EXS provide routing and switching, ensuring full Cisco IOS, network tunneling and call manager support and provides LAN and PoE+ ports. These modules can be stand alone or used in tandem with each other either stacked or unstacked.