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Motorola SB5120 cable modem problem with Netgear RangeMax N

By suirauqa ·
I have broadband cable internet connection from Comcast, who gave me a Motorala SB5120 modem. It works fine when connected directly to my laptop computer (Vista Home Premium) using an ethernet cable. When I sought to put a wireless router in between, all **** broke loose.

The router is a Netgear Wireless N RangeMax Dual band router, capable of sending signal at 2.4GHz and 5 GHz simultaneously, and offers many different types of encryption including WEP, WPA-PSK, WPA2-PSK (AES) and a combination of the latter two. Since my Vaio laptop is capable of receiving signals at 5GHz, I chose that option to receive interference free signals.

The signal flow is such:
Cable -> SB5120 -ethernet cable-> Netgear -ethernet cable-> laptop;
Or after configuration:
Cable -> SB5120 -ethernet cable-> Netgear --wireless-- laptop.

The problem is occurring in both these scenarios. Even after successful connection, where the Netgear Router has cloned the laptop's MAC address, it is receiving the proper IP from cable modem, the cable modem disconnects every 15-30 minutes on its own, and then reconnects after about 5-10 seconds. All the lights go off except the PC activity light, and then start coming back one at a time from top to bottom (This sequence would normally happen if the power to the modem is cut and then restored).

As a result, I am getting very slow speed of connection to almost any web page. As long as the modem remains operational, the webpage load fine, but once it starts to disconnect at regular intervals, the pages slow down to a crawl and then the browsers don't load any page any more, until the modem comes back up.

When I completely disconnected the Netgear router from the equation, and connected just the modem to the computer as before, I had no problem getting on the internet and staying connected. Can someone please offer some constructive suggestions about my problem? Has anyone else had the same issue?

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All Answers

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You need to go into...

The router browser IE: type in the ip address of your router, then it should ask you for a password key (if you have set one up that is), when in the router settings you will need to set the connection to a "0", it will have something like "reconnect every 5 or 10 seconds". Hope this helps you.

Please post back if you have anymore problems or questions.

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Thanks very much for the suggestion...

by suirauqa In reply to You need to go into...

unfortunately, the netgear router browser did not have any such option!
For some strange reason, rather than asking people to type in the usual "http://192.168.1.1", they ask people to type in "http://www.routerlogin.com". Weird!!

My problem was resolved though, on its own! I left a note about it in response to the next post.

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There one glaring error here

by tintoman In reply to Motorola SB5120 cable mod ...

You say that the netgear device has cloned the mac address of your laptop, if that is true this is likely to be the cause of your problem.
The netgear should be cloning the mac address of the cable modem NOT the laptop, once you have established that correctly your router will freely distribute IP addresses and no doubt continuous internet access to any computers connected to it

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Thank you for your reply...

by suirauqa In reply to There one glaring error h ...

but I am not sure that it is wholly correct. From my admittedly limited understanding, the cable modem has to be fooled into believing that it is exchanging data packets with the computer, and not another device in between. Therefore, if the router (being in between) has to get a signal from the cable modem, it has to display the computer's MAC address as its own. Am I incorrect? This has been true for every wired or wireless router that I have worked with, linksys, netgear, and belkin.

I confess that I have not worked with a cable modem before, because wherever I was, at home or at work, the internet connection from a T1 or T3 LAN always came through a wall jack, and that was it. This is the first time that I am having to deal with a cable modem.

Anyway, UPDATE: I reconnected the modem to the router with an ethernet cable, as before, and switched on the wireless of my computer, again as before, and I find now everything is working in perfect order! Go figure! I have not had a single instance of modem restarting for over 22h now!!

UPDATE ON UPDATE: I still have no clue why this happened in the first place, since it works now without my changing any single setting!!

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There is one glaring error here

by tintoman In reply to Motorola SB5120 cable mod ...

You say that the netgear device has cloned the mac address of your laptop, if that is true this is likely to be the cause of your problem.
The netgear should be cloning the mac address of the cable modem NOT the laptop, once you have established that correctly your router will freely distribute IP addresses and no doubt continuous internet access to any computers connected to it

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