Graphing Motorola Surfboard SB5101 Cable Modem Stats with Cacti

So you’ve got a cable modem, and you’re having problems (or you just like to track everything). You’ve already been to the management page of your cable modem (in most cases it is reachable at, but now you want more, or at least to be able to track changes over time. What can you do?

Use Cacti to graph the stats on your cable modem. Man that would sure be easy if you only had SNMP access to your DOCSIS cable modem. If you do then check out this post. But, if you’re like me and you have good old Comcast who disables client side SNMP access then you’re going to need a script to scrape your modem’s web based interface.

Here is my script for a Motorola Surfboard SB5101 cable modem (based off this post) which will display the following two graphs within Cacti:

Cable Modem Power Graphs

This graph displays your power levels and signal to noise ratio.

Cable Modem Frequency Graphs

This graph displays the frequencies on which your modem is operating. These should almost never change.

In order to use these you will need to download two items. The first is my Motorola Surfboard SB5101 PERL script which can be downloaded from my Cablemodem Template post on the Cacti Forum and then upload to your Cacti scripts directory.

The second piece to download is my Cacti XML host template also from my Cablemodem Template post on the Cacti Forum. Once downloaded you can import it and then add your devices.

This is my first custom template. As I create additional ones, I add them. If you use this template, please let me know how it works for you.


3 Techs and Back to Renting

Well Comcast finally showed up 30 minutes after they first called. The first tech got lost, so shortly after she finally arrived, another tech showed up followed by the shift supervisor (the neighbors were most impressed, one of them even got a free service call out of it).

They tested this, and looked at that, they replaced some connectors, made me a new patch cable, made numerous trips inside and out. Finally after all that, my trusty old cable modem wouldn’t even sync up anymore. So they installed a new cable modem, for which I get the pleasure of rent for $3/month. I’ll give it a couple of months, and then decide what I really want to do.

As Slow as Dial-up

Well if you’re reading this post then you are very lucky. In what seems to be a yearly event, my Comcast cable connection is horrible. When it is up, sometimes it is as slow as dial-up, and at best it is at DSL speeds. We are supposed to have a tech out Wednesday evening. Frustrating.

I think the problem is the Downstream SNR (Signal to Noise Ratio). According to Comcast’s site as well as others the number should be above 35 dB. Mine ranges from 27-33. So this combined with a weak signal in general is probably why it is so bad.

I found these details out by getting into the web interface to my cable modem. I have a Siemens SpeedStream 6101 cable modem. You can access the screens by open your browser to and using root as both username and password.