If you have a room full of console servers, each of those machines will require a serial console. However, serial terminals are difficult to acquire and are very expensive. Thankfully, there are plenty of budget solutions that will provide a console server to access when a machine or network breaks down.
A good console server should provide remote access, whether the computers are in your office or on the other side of the world. Logging is also important so you look at the last console commands to see if there were any problems. When the network has failed, that is usually the time where you need a console server the most, so your device should be able to function through remote access even if the network is down.
If you are using PC hardware components for your server, then one possible solution is a KVM switch. This device will allow you to use a single mouse, video screen, and keyboard to control multiple consoles. This technique does not require much space, but it will only function for PC hardware, which means you will not be able to control any communications gear.
KVM switches also lack quality logging and scroll-back options, so you will need to use another method to handle alerting. The biggest downside to KVM switches is that it is will not run with serial-only devices. Therefore, even if you have a room filled with PC servers, you will still need some type of serial console server solution.
Some users may try to use a single terminal console and switch between servers as required. You can either use a serial switch or plug it straight in the required machine. Serial switches are not cheap and it may cause problems when switching between servers.
Serial switching is a good solution if all your computers are based locally, but there are some drawbacks. It can be very difficult to figure out what configuration of DTE DCE headshells are required to match with the hardware leads. It can take several minutes for even an experienced network administrator to match the leads with the breakout boxes, all the while the users are complaining about the downed server. In addition, there are not remote logging or access capabilities.
Terminal Server Hardware
Usually, the serial ports and console server machines are configured for reverse telnet access. This allows users to telnet to a specific IP and be connected to that console server or computer. This technique is very cost-effective and any old terminal server can be used. It is also accessible through the network, providing remote access capability. However, if the network goes down, you will not have access to any console, even if you are sitting in front of one of the machines.