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Recently I started to have some problems with my network connection. After a little time (from 5 to 45 minutes) the connection seemed somewhat dropped. My ISP says that the physical DSL connection is completely fine. The connection between my router and my modem also looks fine. The connection between my PC and my router seems to work too. (I'm not on Wi-Fi.) My router doesn't dial in again. It's just that all my downloads, IM connections and everything like that ceases to be.

I tried to connect trough the modem directly from a PC. If I do that I can't reproduce the issue, the TCP connections remain alive for more than an hour. Because of this my ISP says it's not their problem, it's the router's. I somewhat doubt that because I can reproduce it with two completely different routers. (I have a Belkin and a TP-Link router to try.) I also tried the ideas Google brought up, like making sure that my firmware is up to date and praying that it will work. Without any luck.

Now the question is: how can I test out what problems the router (but no PCs) see with my connection (or vice versa why problem does my connection have with routers but no PCs)? My router logs are not very informative on that part since there is usually no physical disconnection and re-dial. I would really prefer a thorough deterministic way that actually gives me the result over guesswork, because if it really is my ISP's problem I'll need hard evidence to make them work for their money. (And no, sadly simply changing my ISP isn't an option.)

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Since you connected a PC "directly" to the DSL modem, does that mean that the modem has router capabilities (e.g. DHCP, NAT, firewall etc.)? Have you properly configured all of your network devices? Have you examined modem log for clues (you only mention router logs)? Please list the model numbers of the equipment you are using, and how you have configured and inter-connect them. E.G. please explain why you think your "router dials in". – sawdust Dec 12 '12 at 19:35
No, the modem doesn't have router capabilities. No, I don't know if I properly configured everything. No, I don't have modem logs (it's a lame old DLink 350T router). And no, I won't list every single detail and settings of all of my equipment, it would take pages. But I know the dial ins from the router log where it says PPP INFO sent [PAP AuthReq user=(hidden) password=(hidden)]. – ytg Dec 20 '12 at 7:13
up vote 1 down vote accepted

I have seen this issue caused by a power problem or excessive temperature.

You should be able to tell quickly if the router is getting very hot and figure out a way to cool it at least as a test. Given that two routers have this issue heat seems a less likley possibility.

Power is a bit more of a challenge. In most cases I have seen it is a low voltage issue that sends the roouter into a state where lights are on but some or all functions are in a failed state.

A quality UPS would tell very quickly. And a good UPS is never a bad idea.

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Since for some reason the problem doesn't seem to exist now, I'll assume that it indeed was a power problem. I'll accept this answer until I can somewhat confirm it by buying a UPS. – ytg Dec 20 '12 at 7:15

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