What is telnet?
In most cases, the main user interface to a router is its web interface which is accessed via a browser. In this interface the user can configure the router and obtain information from it. The frequently requested 'router stats' can usually be obtained here.
Many routers also provide a command-line interface in which commands can be typed to configure the router or to obtain information. Usually this interface will provide more comprehensive capabilities than the web interface, and should be considered an expert tool. Command line interfaces can also be used remotely, which can be very useful for administrators managing systems on behalf of others. There are different types of command-line interface, but the most commonly used one is telnet. This is not a secure protocol, so is not recommended for remote use, but is very convenient for local purposes.
How to use telnet
Most operating systems including Windows, Mac OS X and Linux include a telnet program in their normal software setup (or it can be easily installed). To use this, open a command line window and type
telnet <IP address>
telnet <IP address> <port number>
The default telnet port is 23, but some routers may use a different port, and in these cases the second form of the command must be used.
The IP address is the same address as you enter in a browser to access the router's web interface; this will be something like 192.168.1.254 - the actual address should be shown in the router's manual, or you may find it on the Kitz router stats page.
After entering the telnet command you will normally be asked for login details (user name and password) which are the same as those used when you access the web interface. If this is all entered correctly you will be logged into the router and will be presented with a > or # prompt. You can now type CLI commands into the router.
It can often be difficult to find out what commands can be used here, because different routers have different command sets. Most manufacturers are rather secretive about this, and there are few published documents to help.