What to do when your cable modem doesn’t work
I got a call from my sister about her internet connection dying. Â Here’s what I do in this situation – my internet is cable modem (CM) and my ISP is comcast.
- Attempt a reset by the ISP. Â Through remote reset, the ISP can re-initialize your router and this may help. Â If they *can’t* remotely reset your router, that seems like an indication that they may need to physically send someone to your home, doesn’t it?
- Gory details: Cable modems function on a standard called DOCSIS. Â You probably don’t hear about this or think about it much but periodically your ISP may start nagging you insisting you need to upgrade your cable modem to a newer model to get the best service. Â This probably means there is a new DOCSIS standard out, or they are offering support for a new standard and unless you get a newer modem, they won’t be able to sell you more expensive service. Â You’ll probably only find yourself in this situation if you choose to buy your own cable modem rather than leasing one from your ISP – and you should almost definitely do that. Â Newegg offers a bunch of DOCSIS 3.0 Cable Modems for under $60 and that’s what you’d probably pay in lease fees after 1 year. Â Plus, why pay Comcast for this?
- Attempt to reset it yourself through power cycle. Â Simply unplug the CM, wait a minute, then plug it back in.
- Waiting a minute may or may not be a magic amount of time (depending on your ISP, your CM, or the service you’re getting from your ISP with your CM). Â Go ahead and wait a full minute though.
- Attempt to get in to the configuration for the cable modem and figure out what’s wrong from the logs.
- If you lease your modem, then your ISP has probably locked this down and you won’t be able to reach it (so go back to 1 or 2).
- Otherwise, it might be http://192.168.100.1 – so give that a try.
- Or, it might be printed on the bottom of your CM so get a flashlight and go try to take a peek.
- Or, you can do a web search for your CM model and probably find its default address that way.
- Assuming you were able to reach your cable modem’s configuration page, as it boots, you should be able to see a few useful bits of data:
- Where, in the connection negotiation process, it is failing. Â This may or may not help
- Signal strength information. Â The two most interesting values will probably be signal-to-noise (should be ~32dB or higher) and power (should be between ~-10dBmV to +10dBmV). Â If your numbers aren’t in those ranges, you probably have an issue with your line connection somewhere and a technician will have to come to the house / line to assess where the problem is
- Full logs. Â If you’re hitting a problem, you’ll probably find your logs end when they hit that snag and you may be able to research based on that information.
I hope this is useful!