Global Configuration Mode

In order to make any configuration changes of substance to a Cisco router, you’ll need to access global configuration mode. Three main global configuration modes are available, and allow you to change the configuration stored in different locations. Noting the differences between the three is extremely important. The three main modes include:

Configure Terminal. This mode is by far the most common one you’ll interact with. Configure terminal allows you to make changes to the running configuration of the router, which you should recall is stored in RAM. These settings are the ones currently being used by the router.

Configure Memory. This mode provides you with access to changing the startup configuration of a router, which is stored in NVRAM. If you choose this mode, the startup configuration file will be loaded into RAM, where it can then be changed. It is generally a good idea to back up the current running configuration to a TFTP server prior to issuing this command – we’ll look at how that is accomplished later in the chapter.

Configure Network. This mode allows you to change a configuration file that is stored on a TFTP server. Again, this file would first be loaded into RAM, then allowing you to make changes. Similarly, a backup of the current running configuration should first be performed.

For the most part, you will be making changes to a router’s running configuration, so you’ll probably be using the configure terminal or config t option. To access global configuration mode, simply enter configure terminal from the privileged mode command line.

toronto-1#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.

Notice that the prompt has changed – the new prompt specifies that we are in global configuration mode. You should also pay attention to the instructions – the section that says End with CNTL/Z actually means that to exit global configuration mode, you should press Ctrl+Z. This command was also covered in the IOS shortcuts we looked at earlier.

While entering the complete command configure terminal isn’t too tough, you can also access global configuration mode using shorthand. In this case, try con t.

toronto-1#con t
% Ambiguous command: "con t"

Again we end up with the ambiguous command message. But why? To find out, enter con? at the prompt:

configure connect

Notice that both the commands configure and connect start with the letters CON. Let’s try going a step further, adding another letter:

toronto-1#conf t
Enter configuration commands, one per line. End with CNTL/Z.

It worked! The command conf is not ambiguous, nor is using the letter T to represent terminal. Just to confirm, take a look at the options available for conf ?.

toronto-1#conf ?
memory Configure from NV memory
network Configure from a TFTP network host
overwrite-network Overwrite NV memory from TFTP network host
terminal Configure from the terminal

Don’t worry about the overwrite-network option. It allows you to overwrite the startup configuration file stored in NVRAM with one stored on a TFTP server. Looking at the end of the output above, notice that one of the options is a carriage return . If you type conf and then press Enter, you will be asked where you want to configure from, with terminal being the default option. Pressing Enter again will automatically choose the terminal option.

Configuring from terminal, memory, or network [terminal]?
Enter configuration commands, one per line. End with CNTL/Z.

To return back to privileged mode, press Ctrl+Z. This will produce the ^Z characters shown. Ctrl commands do not require you to press Enter.


Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.