Home > Digi, Hardware, Home Lab > Using a Digi CM32 Serial Console Server

Using a Digi CM32 Serial Console Server

For my home lab, I was looking for a Serial/Terminal Console server.  Needs weren’t terribly fancy – had to be accessible via TCP/IP, should let me do HTTP/HTTPS authentication against it, should let me do Telnet/SSH against it and/or devices connected, needs to be rack mountable and above all else, should be cheap!

After some digging, I found myself a Digi CM32 Serial Console Server.  1U Rack mountable, uses RJ45 cables to connect to RJ45-DB9 converters.  Allows use of HTTPS and SSH.  With it, I can connect to my serial devices by using SSH to the IP of the CM32, and using ports 7001-7032 to connect to ports 1-32 respectively.  What more could a guy ask for.

I started by looking cheaper/smaller – all I really needed was 8 ports.  But it would seem that supply and demand has provided for a considerable abundance of these devices on eBay in the 32 port range.  You’re likely to pay 2-5x as much for a 16 port!   While you might find these for $500, you can often find them for < $60, $100 with shipping to Canada.  The only thing you’ll need to go with them, is the RJ45-DB9 converters – best price I found was on Amazon (http://www.amazon.com/gp/product/B00008CMLM/ref=oh_details_o00_s00_i01) for Model Number 7600071 CM Cable Adapter – which SHOULD be an 8 pack of the adapters.   So if you don’t factor for the RJ45 cables, the cost to do 8 devices was under $200 with shipping, or about $25/device.  Can’t really go wrong at that price!

An important link to have – Product Support: http://www.digi.com/support/productdetail?pid=1859&type=documentation This includes documentation, the latest firmware (May 2010), etc.  While the firmware may not be that new – what does the device really need to do?  It’s just converting TCP/IP to serial, and that’s been around since dirt.

I won’t get too much into the configuration here, as I’ll try to do that once/if I get RADIUS authentication working on it.  General TCP/IP setup is like any appliance.  The only thing that really matters is configuration of each serial port.  You simply want to tell it the port speed/parameters and then the connection method:

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The connection method is where you can tell if if you want to allow to Telnet or SSH to a custom port, and translate that through from your workstation:

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The “Listening Port” is automatically configured, but can be over-ridden.  The “Protocol” is where you can toggle between Telnet and SSH or RawTCP.

Once that is saved, then you can fire up PuTTY (or your tool of choice) and enter the IP of the device and port (ie: 10.0.0.91 and port 7002 for Port 2):

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Once you connect, you authenticate against the CM32 first, and then are dropped to the console of that particular device – in this case, Switch 2 in my PC6248 stack, which ended up being the Management Unit:

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No more trips to the basement!  (Well, assuming I find a cheap switched PDU, that works 0U in a 24U half rack….. ha!)

Forget just for a Home Lab – for < $400 you’d get about 32 ports worth in an office environment.  Old?  Yes.  Out of warranty?  Certainly.  Technology older than dirt, so it doesn’t matter?  Yup.  I’d have killed for a few of these in the office!

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Categories: Digi, Hardware, Home Lab
  1. May 18, 2013 at 2:52 PM

    I have a Digi CM 32 I just cant figure out which cable I need to use between Digi CM’s Terminal Ports 1-32 and between my Cisco Devices Console ports? Any idea? pinouts?
    I tried Cisco Rollover console cable RJ45 on both ends, Patch cable , Crossover Cable.. None worked so far.. (May be cable error tough but could be a rare one..)
    Thanks

    • May 18, 2013 at 3:04 PM

      As far as I know, a normal RJ45 patch should work as they’re designed for cisco equipment to be native. I’d have to check.

  2. Patrick
    February 26, 2014 at 3:54 PM

    I decided to buy a cisco home lab and my favorite CCNA site suggested a Digi 32 cm for my Terminal Server. I followed your guide and I have SSH into the Digi but it does not drop me into the CLI of my device. Any suggestions ? I have screen shots of where I am at if you need to see saved as a PDF. I am just looking to get this working correctly.

    • February 26, 2014 at 4:16 PM

      On mine, to reach a particular device, I would SSH to the IP of the device but utilize a custom port of 70xx where xx = port number. So port 01 of the CM32 would be ssh://nw-cm32a:7001, and port 16 would be ssh://nw-cm32a:7016. If you’re using the default port of 22 for SSH, you’ll receive the console of the CM32 itself, and not one of its ports.

      Let me know if that works, if not I’ll find a Cisco switch and see if there’s something off about how they work, I don’t have one in my lab currently.

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