What are KVM switches? KVM stands for Keyboard Video Mouse - do not confuse with Linux Kernel Virtual Machine. These switches are hardware solutions to operate several computers or servers from a few numbers or even only one user set keyboard/ monitor/mouse. This keyboard/monitor/mouse set is called console. This goal is reached without any special software running into connected computers.
What is an IP KVM switch? IP KVM switches allow you to access their console port, or one of their console ports, remotely through a TCP/IP access. It may be simply from another room over your LAN or from anywhere in the world using the Internet. Users take remote control of computers or servers by using a web browser or a small software utility similar to remote control software tools. The major differences with remote control software are that IP KVM's don't need a server program running into the computer, the control is possible even at BIOS level, and it is generally possible to power off and power on the computers under control.
How does a KVM switch work? On computer side, the KVM switch emulates a monitor and a PS2 and/or USB keyboard and mouse set. Thus, each computer or server "thinks" it is connected to a keyboard, monitor and mouse at all times. On the local console side, the KVM switch drives the standard keyboard mouse and monitor in the same way as a computer does. When you select a computer, its video, keyboard, and mouse ports are replicated on the local console ports allowing you to operate the computer normally. Some KVM's can switch the audio ports.
KVM operation: Most of time, several methods permit to configure and to operate the KVM switch: front panel push buttons; special keyboard strikes or "hot keys"; on screen display (OSD) menus.
Cables: All attachments can use special cable assemblies or simple twisted-pair cat5 cables.
Remote access: Most of time, console peripherals are connected directly to the KVM switch, limiting the user installation area to a few meters. To expand the user area, the consoles can be attached remotely, up to a few hundreds of meters with cat5 cable, or farther by using a TCP/IP local or remote connection.
What are the characteristics of a good KVM switch? KVM switches are complex devices that vary a lot in quality and performance. Lower price switches often show poor video quality, poor USB and PS2 emulations, wrong video bandwidth figures, and tiny controllers incapable of providing simultaneous emulations on all ports. You get what you pay for. A good KVM switch is characterized by:
- the quality of USB and PS/2 emulations that will make it compatible with all computers,
- the quality of the video switch that must handle hundreds of MHz without spoiling the video,
- the nonexistence of cross talk between computers,
- the ability to plug new peripherals and new computers alive with automatic configuration,
- the keyboard and mouse emulations maintained under all conditions, even if the KVM is powered off,
- the handiness of commands and hot keys to spare user fatigue,
- the speed of switching process, to not wait 10s for video and peripherals coming back after each switching,
- the quality of On Screen Display menus,
- the capability to cascade or daisy-chain several devices to increase the overall capacity of the system,
- the protection of ports against transients and over voltages,
- the possibility to update the firmware