A method of remotely managing the wide area network (WAN) telecommunications components of your network by using a secondary serial communication link. These devices are typically routers, switches, or Channel Service Unit/Data Service Units (CSU/DSUs) that establish and maintain WAN links to the corporate network. Devices that can be managed out-of-band usually have an RS-232 port or some other serial port for remote control of their functions.
In a typical setup, a remote PC is connected by a modem through a phone line to a code-operated switch located at the office local area network (LAN). This switch controls networking and telecommunication devices such as routers, bridges, switches, CSUs, and even power supplies through their RS-232 serial connections. Alternatively, the modem might be connected directly to a remote modem connected to the device being managed.
In either case, the result is a separate low-cost dial-up circuit connecting the administrator and the network devices that is independent of the main network connection, which is usually a more expensive T1 or other leased line. The administrator can thus access the WAN device from a remote location even when the WAN link itself is down, and can troubleshoot the problem from off-site.
Out-of-band management (OBM) also allows administrators to access and configure WAN devices without disturbing the WAN link itself. In other words, OBM functions out of the bandwidth.
Graphic O-7. Out-of-band management (OBM).
For example, you can use OBM functions on a power supply to remotely reboot or reset your network devices when they go down. You can use out-of-band switches to select different serial interfaces remotely over a modem by issuing simple ASCII commands to different devices. You can even use OBM to remotely configure and control devices on your network. OBM devices are a useful part of a network disaster recovery plan.
For networking devices that you can configure and troubleshoot using out-of-band connections, you usually perform management tasks by connecting to a serial port (also called the setup port or configuration port) either locally with a cable or remotely through a modem. You usually use text-based commands from a terminal emulator program such as Windows HyperTerminal, which can emulate a VT100 terminal. You can often control access using passwords for extra security.
OBM offers an advantage over in-band management systems such as Simple Network Management Protocol (SNMP) management systems. SNMP employs the network itself for communication, so if the WAN link goes down, the remote station cannot use SNMP to determine the problem because SNMP functions only if the WAN link is working.
OBM is often used as a backup system for in-band SNMP management, when the devices have limited SNMP support, or when the cost of an SNMP management system cannot be justified. You can often manage a device in-band by using a remote Telnet client for entering the same commands that are used in OBM.
You can often use out-of-band transmission so that a device that enters a problem state calls an administrator’s pager via a modem. The administrator can then dial in to the device remotely and correct the problem. Some network devices include built-in modems and data switches for remote OBM.