Please help me troubleshoot my cable modem - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 11 Old 07-19-2014, 04:37 AM - Thread Starter
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Unhappy Please help me troubleshoot my cable modem

During college I or a roommate owned our own cable modems. I admittedly didn't know much about networking, dchp, etc, but we often had problems with internet drop outs.


For years since then I've leased a modem. The two or three I've been provided have worked perfectly. For a long time it was free, then $3, and finally this spring it hit $8 a month and I said no more - time to buy my own.


So I bought a Motorola SB6121. I use it in combo with a Belkin F5D8236-4 v2 (01) router that I've used since 2009.


I've had so many drop out problems. Various web pages will just temporarily fail to load. After a few minutes refreshing the page opens it without a problem. Here is exactly what I'm getting:








The error is always "The remote computer isn’t responding to connections on port 443, possibly due to firewall or security policy settings, or because it might be temporarily unavailable. Windows couldn’t find any problems with the firewall on your computer. " Or it will list port 80 like it just did a few minutes ago when AVSForum failed to load.


Things I've done to troubleshoot:
-completely reset Internet Explorer. Its not an IE based problem - it happens on Chrome too.
-changed the DNS servers inside Windows
-changed the DNS servers in my router
-completely reset my router
-tried bypassing the router and plugging my htpc direct to my modem - I get ZERO connection to the net. My Windows XP netbook connected fine.


Other relevant info:
-when a site is hanging I can ping it at the command line with no packet loss
-when its hanging directly typing an ip address doesn't work (telling me its not DNS related)
-When a page is failing to load in IE it fails in Chrome too. However, I seem to be able to open the pages on my wifi connected netbook. I haven't used the netbook enough to replicate the problem there.

My assumption is that either 1) I just got a crap modem, or 2) something else is set incorrectly somewhere deep in the Windows set up. Comcast tech support said I have a good signal and its a Microsoft issue. Then problem is that the very arbitrary nature of the dropouts makes it tough to troubleshoot.

I tried to add all relevant event logs and summaries but the forum software doesn't like XML and ETL files. The text ones submitted fine. I tried numerous ways to get a tracerpt dump file onto the forum but it keeps refusing it, not matter if I try uploading txt or I try copy and pasting it. If it could help someone ill gladly send it.


Any ideas would be greatly appreciated. I guess id like to start with why my pc cant get online when connected directly to the modem.
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post #2 of 11 Old 07-19-2014, 05:36 AM
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After looking through the Motorola manual - have you followed the steps listed out on pages 10-12? Did you verify the IP address by running ipconfig through a cmd line?
What kind of hardware are you running? Do you have the latest drivers for your NIC card?


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post #3 of 11 Old 07-19-2014, 07:37 AM
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Are the lights on the front of the modem showing normal operation? These are my SB6121 lights, top to bottom:
Solid Green
Solid Blue
Solid Blue
Solid Green
Blinking Blue

Bypass your router, connect a PC directly to the modem, Reboot the computer. Can you get to the modem config page through browser http://192.168.100.1/
Status Page should say all "DONE" or "OPERATIONAL"
Signal Page Downstream should have SNR 36-37, Power Level should have -12 to +12, Upstream Power should have 50

If you have all of the above then the Modem is working and you have a problem with your router or NIC or PC drivers....

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post #4 of 11 Old 07-19-2014, 07:54 AM
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^ good advice from @hammerdown .

The timing of things (that it didn't happen until you switched modems) points to something weird with the modem, but the symptoms sound more like something wonky with AV/Firewall software. The problem appears to be port specific (you can still ping the web server even when you can't get traffic on port 80) If it's only affecting specific pages (You can't pull up AVS, but Google opens fine) It almost has to be AV/Firewall related as I can't think of anything else that would specifically block traffic on port 80 to a specific site.

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post #5 of 11 Old 07-19-2014, 08:26 AM
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The diagnostic web page of the modem is at 192.168.100.1 Check your signal strength and look at the logs for reboots.

If you want to try connecting straight to the modem, you will need to reboot it. The modem has a DHCP server as well and is locked onto the MAC address of the router.

Since you can still ping and connect with wireless, it doesn't sound like a modem problem.

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post #6 of 11 Old 07-19-2014, 08:42 AM
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Replace the router. It's ancient. Most problems occur at the router level and not the modem because that's the easiest place to hit with DDOS attacks. Many older routers do not have protection from the latest attack techniques and can easily be locked up if you're running things that use UPnP like torrents.
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post #7 of 11 Old 07-19-2014, 08:49 AM
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I know you said it wasn't dns, but I had those same symptoms when I tried assigning opendns servers in my router. I switched to Google DNS servers instead
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post #8 of 11 Old 07-19-2014, 09:44 AM
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From what I understood you said, you can ping the address fine even when the web pages don't load, also another (xp) machine works fine, and you are having trouble with page loads from a browser. Usually when I see this (especially if the other computer is working fine) as said, it would be AV/firewall but also viruses/malware in general. I'll often see this when one was recently removed but not everything it did got fixed.

As mentioned, the modems diagnostics pages should be at 192.168.100.1 if you really suspect the modem. I like to see power levels of downstream within +/- 7, SNR >32... upstream power level should be under 50 (the cable company would have to see the SNR there)... The new modem isn't that bad as it is a D3. One thing that happens with D3 modems is to bond channels properly, their levels must be fairly close (I think within 2 but preferably 1) If they go too far from each other, the modem will no longer bond... the newer 8 channel modems may have 2 distinct ranges that have to be close. When you bypass the modem, after you move the network cable, generally you must turn it off for 10 seconds or so so the MAC address associated with the connected device can be flushed and allow the connection of the other device.

I would also check out that ancient router for a few reasons first is 10/100 ports even some of the early gigabit routers had trouble on the WAN port as it wasn't gigabit and had trouble with anything over about 15-20Mbps so if speeds recently increased in your area, this might have contributed. Lately I have been having a lot of old networking equipment fail because of power supply issues... particularly MoCA equipment but also modems, routers, switches and tuners.

As for DNS, that is usually one of the first things I switch, however since you can ping DNS should be working fine
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post #9 of 11 Old 07-19-2014, 10:31 AM - Thread Starter
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I really appreciate all the great suggestions. And I think I might have actually fixed it, though because of the random nature I wont celebrate yet.

-all the modem signals are within the ranges described and the lights are lit correctly
-my ip address in the LAN properties is set to auto and theres no problem in the command prompt

Whenever I had to connect direct to my old modem I never had an issue. That doesn't happen with this modem, but I never tried rebooting it.

The Windows Network Diagnostic eerrors all reference a firewall and a few of the posts made mention of it too. I definitely don't have one set up in Windows (no antivirus software either) and I thought I had it shut off in my router config settings.

When I got the modem I decided to completely reset my router (I was still using WEP - lol!). In the process of doing that I think the firewall settings defaulted to ENABLED and I overlooked it. Shut it off and I've been browsing for a while problem free. Port forwarding for Ceton and Plex are up too. Pages seem to load more quickly (I noticed too that problems tended to happen most often on media heavy sites like youtube and blip - pages would only half load in those cases).

Thank you all so much. If this fails to hold I will disconnect the router and reboot everything.

I know 5 years for a router is a lifetime but I didn't really think of it as having any shortcomings (for me at least). How often do you guys replace yours?

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post #10 of 11 Old 07-19-2014, 10:37 AM
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Quote:
Originally Posted by pittsoccer33 View Post
The Windows Network Diagnostic eerrors all reference a firewall and a few of the posts made mention of it too. I definitely don't have one set up in Windows (no antivirus software either) and I thought I had it shut off in my router config settings.


This will get interesting.

RAID protection is only for failed drives. That's it. It's no replacement for a proper backup.
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post #11 of 11 Old 07-19-2014, 10:45 AM - Thread Starter
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Ive been firewall and antivirus free for 10 or so years - do you really think its that important? I don't do torrents or use this pc to type or house sensitive data (no bank logins or bill pays).


The best you could get breaking into my PC is episodes of Miami Vice and some Michael Bay movies

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Mironto's Panasonic plasma black level restoration guide
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