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I have a problem which is driving me crazy as it does not make any logical sense.

For some reason yesterday, the internet connection went down. Everything pointed to a defected router and therefore I bought another one.

I stripped all the RJ45s from the network as there was a switch in place as well so I wanted to make the network as simple as possible.

This is a cable connection with a static IP and thus I tried the most basic thing of all to verify that the cable modem is actually working. Hence, I changed the IP, Subnet Mask, Gateway and DNS servers to point to the static ones provided by the ISP (this worked).

Then I tried connecting the cable modem with a PC and the new router. I configured the router to use the static IP however I could not get an internet connection (router kept saying connected/disconnected) but I could not connect once from the PC.

Utterly amazed, I tried the old router (the one presumed bad) and checked the settings. Again utterly amazed, I noticed that the last octed of the static IP was incorrect (I cannot understand how there was an internet connection till yesterday as routers don't just change their settings...). I though that this would solve the problem and I changed the static IP to the correct one but it still did not work!

I changed the router again to the new one, did a factory reset and nothing. I changed the router again to the old one, did a factory reset and still nothing!

I then reconnected once again the modem directly to the computer and it worked.

I also tried connecting the modem to the switch and the switch to the PC and this worked as well.

I even tried changing the cables as I though one of them was not good but that was not it either.

Needless to say, this does not make sense and I don't think that I encountered a problem this weird.

My only conclusion is that something is wrong with both the old and the new router. I saw some reviews on the new router which they bought (as I did not buy it) and there were some negative reviews but I still think that it is a great coincidence that both routers are not working properly. But apart from that, since the switch worked as well, what else can it be?

Please if anyone ever encountered a similar problem PLEASE help me as I don't know what else I can try.

Thank you

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Did you power cycle the modem between all these network changes? A modem I got one ISP had limitation in the firmware, that would only accept activity from a single device. Where that device was identified by the first MAC address the modem saw after it was booted. So whenever you changed the device connecting to the modem, you had to power cycle the modem. –  Zoredache Jan 11 '13 at 21:00
    
sounds silly saying it but are you using the WAN port on the routers physically and setting the WAN settings for the IP? Or are you accidentally changing the LAN address instead or plugging cablem modem into one of the LAN ports? –  TheCleaner Jan 11 '13 at 21:03
    
Yes i have a preconfiguration for static connection and that is what i chose... –  Chris Jan 11 '13 at 21:08
    
You shouldn't need to configure your static IP address. Your ISP should assign it to your modem automatically and your modem should assign it to your router automatically. (Make sure your router's LAN IP address doesn't conflict with it's WAN IP address. The LAN IP address should be something private, like 192.168.0.1.) –  David Schwartz Jan 11 '13 at 21:22
    
Zoredache. you were right. That's the only thing which I did not do! I switched off the modem, router and pc. I then switched on the modem, waited for it to load, then did the same with the router and finally I switched on the PC. Worked like a charm. The thing which still amazes me is the fact that this problem started with the fact that the static IP got changed in the router's configuration. Anyone encountered something similar to this? David Schwarts, no I had to configure it manually. Zoredache put your comment as an answer so I can accept it. Many thanks! –  Chris Deguara Jan 11 '13 at 21:37
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