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I'm new(ish) to networking and have been setting up a home server. Part of making sure the server is good and healthy is making sure it has a solid Internet connection.

Unfortunately, our DD-WRT router jams at least weekly and needs to be reset. No one uses P2P on our network; at most only a few standard machines are doing basic web browsing at any given moment.

Last night I got an opportunity to look for the root of the problem, and try to restore the Internet connection using a less-aggressive method than restarting the router.

I ping(ed) 8.8.8.8 (a Google Public DNS IP address), but received no replies. Then one of the other LAN users insisted I fix the issue right away. However, instead of restarting the router, I made it release and renew its DHCP lease, and the Internet connection worked again.

Leaving the router's WAN port, the next machine down the line is the cable modem, which connects to Comcast's wires. We had similar symptoms with the last three routers, all of which were Netgear or Broadcom machines; the last two ran DD-WRT.

So I have three questions:

  1. Who is at fault? ISP or DD-WRT?

  2. What tools can I use to more intelligently diagnose the problem than checking whether a known server like Google's DNS is reachable?

  3. How can I make sure DD-WRT takes care of this problem itself, even if I can't fix the root cause. For example, I have considered writing a script that pings a known server, such as 8.8.8.8, at regular intervals. If no response, a log is made of how far the machine makes it (using tools like question 2), and then the DHCP is released/renewed. I feel as though a more elegant solution should exist.

A876
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lakechfoma
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2 Answers2

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I have actually run in to this exact same problem myself, several times. (In one case the problem turned out to be an improper power supply on one of my routers, so much sure you check ALL the basics first.)

  1. As for who's at fault, I would blame consumer level equipment. These little Netgear/Linksys/etc boxes have never been the bastion of reliability, and there's also nothing elegant about them.

    • Check your WAN IP address. I've had junky modems temporarily hand out a 192.168.100.x address to my router while it picks up a proper IP address. Sometimes my router would get stuck here, rather than picking up the public IP.
    • If you want to drill down in to what's going on there, shove a hub (not a switch) in between the router and modem, then sniff the packets from a computer using Wireshark or Microsoft Network monitor.
    • You could also use tcpdump from your DD-WRT router for troubleshooting
    • It can also be helpful to enable logging on the DD-WRT router and take a look at what events pop up.
  3. Personally, I would stop fighting with it and go ahead and set up your script. Check 8.8.8.8, release and renew if that's down, and if that doesn't work reboot. Problem solved. If the problem isn't solved, smash your modem in to tiny little pieces and get a new one.
rtf
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3

As noted by @r.Tanner.F , consumer-grade hardware can have issues.

One of the most common is they do not tolerate heat or bad power well.

Make sure there is ample air circulation and avoid stacking other hardware like modems or switches.

Power is best addressed by installing an UPS so that you get a steady 120V (or 230V). I have seen many clients with issues solved with a good UPS. Spikes are usually not the issue but rather brownouts and low voltage in general. It seems to send the device into a weird state where it may not work at all or some functions fail.

In any case, a good UPS is always a good idea.

A876
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Dave M
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