I have a Motorola modem SURFBoard SB4200, along with a wireless Linksys router that connects to that modem. The router works normally but the modem often dies and restarts itself after about 1-2 minutes.

What could be causing this problem? How should I start debugging it?

Could an excessive amount of network traffic be bringing down the modem? Are there any tools that can monitor the modem?

BTW, I use internet cable service provided by Comcast.

  • 1
    If the modem is provided by Comcast, have you contacted them for ideas or replacement? Sounds broken though. :( – Ƭᴇcʜιᴇ007 Sep 5 '11 at 7:04
  • I know there are issues with some ADSL2+ modems where they are limited to a certain number of TCP connections and they freak out and lockup and then restart after they are overloaded. I saw this with a lot of broadxent modems being used with torrents. I would heed techie007's advice and contact Comcast through, they'll have a list known issues or steps to troubleshoot and replace the modem if it is indeed bad. – MaQleod Sep 5 '11 at 17:22
  • I actually replaced the one provided by Comast with this one. So, I guess they would not provide technical support for it. I don't use bittorrent, though. I wonder how I can login to the modem to check the log or something. I connect my MacBook to the modem using USB cable trying to read its logs but the modem is not shown in the MacBook. The modem has address 192.168.1.x, the wireless network has address 192.168.2.x so I can't remotely login to the modem through browser. – chepukha Sep 6 '11 at 7:03

there is a feature called 'IP Flood Detection' that needs to be disabled. (It is located under the Firewall page) By default, it is turned ON. When ON, this feature eventually causes everything to slow to a crawl and randomly reset modem. Turn it OFF (uncheck box) This is certainly a failing on Motorola's part to default a poor-functioning feature ON in the first place.


That sounds like an old modem from the DOCSIS 1.0 & 1.1 standard era from my search on your brand & model. DOCSIS 3.0 standard modems were released in August 2006, according to Wikipedia. You may be handicapped with that SB4200 modem and it is tripping up on new ISP protocol delivery standards, thus the constant reboot? A simple question to Comcast's tech support regarding DOCSIS 1.0 & 1.1 support in 2011 might shed light on compatibility issues or known problems. They should have a list of compatible modems as well, yet probably not a complete list.

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