Update: You may also want to read this after this article…
Ever needed to use a USB to Serial adapter to telnet in to your Cisco Console on a Mac OSX and gone… Ummm… I might use a PC instead. Well fortunately it is way easier than you may think. It just isn’t quite as intuitive as it should be.
We will assume that you have a USB to Serial adapter that shows up in your /dev after you install it. You may need to download a driver, and for some chipsets I have not been able to get them running on Intel OS-X (Phillips/MCT chipset in particular. The Belkin F5U409 is one of these). I found the UC-232A type which use the Prolific PL2303 chipset, plugged straight in and worked with very little effort and a straight driver download.
Suffice to say if you ls /dev and see a entry like tty.PL2303.xxxxx all is well. It is worth copying this to the clip board as you will need it in a moment.
Next comes the wonderful screen command. Man screen will give you a little more info, albeit, fairly sterile and confusing, but information none the less. Goolge it to give you a better insight.
Hook your console cable to the USB – Serial adapter and the router and then from a terminal window simply type
screen /dev/<Insert device name here> 9600
(obviously this bit is whatever your device is called) and hey presto, you are consoled in to your router.
Now it does have some gotchas. I am used to using <Ctrl>+A to move to the start of the line for when I forget to use “do” or general typos, but <Ctrl>+A is screen‘s primary command. You issue it prior to all other screen commands. So for example if you go <Ctrl>+A and start typing do in a screen session, you will only get as far as the d and your screen session will disconnect, as <Ctrl>+A+D is the screen command to disconnect the session. You will then need to type screen -r to reconnect to the session.
So, it is not a Telnet or even ssh Session. But it is very useful…
Update: Grrrr… I updated my SL MacBook Air to Lion and the Serial Console Cable would no longer work. See my new article on what I had to do to fix it.