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SB8200 fails to connect immediately after power cycle

  • 7 May 2024
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I purchased a new SB8200 (and TP-Link router) to replace a COX Panoramic combo modem/router that I was renting.  

I have one problem:  the SB8200 will not reconnect when power cycled.   Specifically, unplugged, then plugged back in.  The send and receive lights will go solid green, but the online light just blinks.   Eventually (minutes), the modem appears to restart and the lights cycle through startup phases, resulting in the same status described above.   It seems like the modem will do this forever (I give up after 30 minutes).   Using the management webpage, it appears each reset cycle is using an different set of channels to attempt the connection.

I only way I’ve discovered to get the SB8200 to connect is to leave it unpowered for several minutes (like 10), then plug it in.   Only then will it successfully establish a connection.

I’ve validated that all signals levels are good (per the SB8200: CABLE SIGNAL LEVELS FAQ).   I’ve had COX at my house, and they’ve verified my cable service is within spec.

Do have a bad modem?    Or is this standard behavior for this product?   

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Best answer by SURFboard Moderator 10 May 2024, 23:05

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In this case we would suggest you to perform hard reset on the modem then that will configure the modem to work without any issues as a fresh new device so after resetting monitor connection for next 24hrs.  please, disconnect the coaxial cable from the back of the device? At the back of the modem, in the middle section you will see a small hole, inside that hole there is a button, and that is the reset button, please insert a paper clip or a tip of a pen and hold it for 15-30 seconds until all your lights go off, afterwards connect the coax cable back and wait until your device fully boots up.

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I’ve tried multiple hard resets, one while on the phone to Arris support.   It doesn’t resolve the problem and forces me to connect a cable to the modem directly afterwards so I can reset the admin password to something other than the default (again).

I was really hoping for a DOCSIS connection protocol expert to weigh in here with some insight to what might be happening…

BTW, I’ve had no luck with Cox either.    They have had me check the connection, cycle power,  hard reset the modem - all the standard frontline help line stuff.   They also sent a tech to my home and he observed the behavior (good and bad).   He suggested I get a new modem.  I figured I’d give this a shot first.

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Could you help us with the IPV4 address?

Connect the modem to the computer directly through hardwired, and please press the Windows button + the letter R on your keyboard to open the “Run command” box.

Once you press the buttons, you will get the little run box. in that box, type "CMD".

Afterwards, you will get a black screen, On that black screen, type ipconfig/all

Please press Windows button + the letter R on your Keyboard to open the “Run command” box.

Once you press the buttons, you will get the little run box. in that box, type "CMD".

Afterwards, you will get a black screen, On that black screen, type ipconfig/all

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Do you want me to perform this action when the modem is connected (i.e. working) or when it’s not connecting properly?

I feel I need to remind you that my problem only occurs when I unplug the modem and then plug it back in, with little time in-between those actions.    If I wait several minutes before plugging it back in, the modem will usually transition to connected.  It been running fine (connected) for a solid week.   I just can’t power cycle it and expect it to connect unless I leave it powered down for several minutes.

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To investigate or further assist on this issue, I suggest visiting www.arris.com/consumersupport.

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