Cable modem spontaneously resetting?


Feb 10, 2012
Hello everyone, I've got a problem that's got me stumped.

Firstly, my network setup looks like the following simplistic diagram:

www(internet) ----- cablemodem ----- apple airport ----- router ----- my pc

Now the problem, which started about a week and a half ago, is as follows:

My cablemodem repeatedly (seems to) reset(s) itsself. I.e. I lose the internet connection on my pc (still connected to the network but no internet connection) for about 10-20 seconds after which the connection restores itsself. This happens in differing intervals, sometimes I can go for more than an hour without disconnects, sometimes I get disconnects with intervals of about 15 minutes.

If I go look at the network setup (which is in the cellar), during the disconnect, I can see that only two lights on the cable modem are lit green and if I wait I can see the modem going through his startup procedure until all the relevant lights are lit correctly and connection restored. Now the cable modem is supplied by my ISP and the closest I can find to manual for it is a datasheet that doesn't help me that much, but the two lights that are lit that I spoke about are the standby light (indicating that it's on) and the network light (indicating that he's connected to the network).

This leads me to believe that it's my cablemodem that is resetting itsself (I could be wrong though).

So one could conclude: faulty power supply (or something similar).

Well, the thing that's got me stumped is that it only seems to happen under specific circumstances, namely when I'm playing Star Wars The Old Republic (an MMO) or when I'm Skyping. Alternatively, it only happens in the evening (the times I'm on my PC), it can go a whole day without disconnecting (I've monitored it with pingplotter)

Other observations:

Every time the connection is restored, the cablemodem gets a new public IP adress assigned to it. This is strange because if I unplug the cable modem and plug it in again I normally keep my IP adress, it's only if I keep it unplugged for longer that a new IP adress is assigned.

This started happening about a week and a half ago, when on wednesday evening I lost my internet connection and it would not start up again (the cable modem indicated that it had no connection to the internet (it had in- and outgoing connections)). I said to myself, fine I'll just call my ISP in the morning but the next morning the connection to the internet was restored and everything looked ok.

Pingplotter gives me quite a bit of packet loss (30%) when put on the ISP's website adress ( I don't know if that's normal (maybe ISPs block pinging to protect themselfs from DOS attacks?) or if it's because I don't know how to use pingplotter? When I do a regular ping I get no loss.

Well, I think most of it's laid out here, so if anyone could shed some light on this conundrum I would be most appreciative. How would I go about diagnosing and solving my problem? Do cable modems get stressed more if there is a lot of throughput? I don't want to call my ISP immediately because I'd like to be semi-sure what the cause is and I'd like to be able to point out where the problem is (because most probably they'll send a technician, everything will look ok and I'll be no further).


Its possible the modem is just getting a low signal and dropping the connection every so often. I would call your ISP and have them come check the lines.

Really I can't think of what else would be causing a cable modem to reset like that, other then weak signal.