Connecting to Cisco devices
In order to start working with Cisco equipment, you first need to configure it by connecting to its CLI through the console. Let us take a look at a situation in which you have an administrator workstation and console or rollover cables available somewhere close to the equipment that you want to configure.
1) Configuring Cisco equipment with the use of a console cable
In order to configure Cisco equipment through consoling into its’ CLI, you need to use the blue cable that is shipped with each Cisco device. This cable has to be connected to the COM port of the administrator’s workstation on one end, and the console port of the Cisco device on the other (the interface is marked with “CONSOLE” or “CON” lettering)
Modern PCs and laptops often don’t have the COM port installed. In this case, you will have to purchase a USB to COM (RS232) adapter.
I recommend using the free and simple terminal emulator Putty in order to console into your equipment (Download from the official site). After downloading it, just run the program (it does not require installation) and change the default “SSH” connection type to “Serial” in the dialog box that opens (see the screenshot below). Click “Open” to start your console session.
If you are using the USB to COM adapter, the “Serial line” value may be different from “COM1”. You can check this in the Windows Device Manager, under the “Ports (COM & LPT)” section. If you see that your port number for “Communications port” is different (for example, it is labeled as “COM7”), then change the value in the “Serial line” box in Putty to your value from the Device Manager.
When your Cisco device is powered on and connected to your workstation via the console cable, clicking the “Open” button in Putty will take you to the device’s CLI. If the terminal window is blank, press “Enter”. At this point, your device should output a greeting text, login request or the CLI itself.
2) Configure a Cisco device using a Rollover cable and another router
In some cases it is possible to gain console access into a device through the use of another, already configured, Cisco router and a special “rollover” cable. I am going to call the unconfigured device, the one you just took out of the box, the “new router” and the one that is already configured and is accessible via a remote terminal, such as Telnet or SSH, the “old router”.
Rollover cables are not shipped with Cisco equipment, but they are very easy to make from a regular patch cord cable. All you have to do is cut off one of the connectors of a regular patch cord cable and rearrange the wires, so that they are a mirror reflection of the other RJ-45 end. To make it more clear, here is a diagram displaying a “mirror reflected connector”:
The wires in the cable must mirror the other end precisely.
In order to console into the new router through a rollover cable, you need to connect the AUX interface of the old router (color coded in black) to the CONSOLE port (color coded in blue) of the new router, using the newly created rollover cable.
On the old router, the one that is already connected, you need to enter the Privileged mode (the hash symbol “#” is displayed after the router’s name. To learn more about various configuration modes, check out this article). Once in privileged mode, enter the following configuration:
line aux 0
transport input all
After this, enter the following command:
telnet х.х.х.х 2001
Where x.x.x.x is the IP address of any interface on this router (the old router).
For example, if your router has an interface configured with the IP address of 192.168.1.1, then you can console into the neighboring new router by entering
telnet 192.168.1.1 2001
Sometimes at this stage you will be asked for a password
- This might be the password for the old router, from which you are consoling into the new router (a password for entering itself, if one is set)
- This also might be a password for the new router, to which you are trying to console, if one has been set at the factory
After entering the required password you will land at the CLI of the new router and can start configuring it.
3) Remote access
The most comfortable way to configure a device, though, is through a remote terminal, while sitting comfortably at your desk. Check out the article “Accessing a Cisco device using the SSH protocol” in order to learn how to do this in a quick and secure manner.
This article was written by Alexey Yurchenko