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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.