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Router(s) fail to connect to cable modem

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New Poster

Router(s) fail to connect to cable modem

I'm facing one bizarre problem.

Cable Modem (Arris SB6183) seems to be connecting to xfinity fine. Xfinity sees it and reports no problem. 

I can connect my computer directly to the Modem using ethernet cable. 

However, none of the 4 routers I tried can connect to the modem over Ethernet. They just blink the red/orange lights meaning "I see ethernet plugged in but cannot get an IP".

To be sure I ran to nearest electronics store and bought new modem and new router. Same deal.

And I did experiment with multiple ethernet cables.

Any idea what can cause that? Thanks!

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Silver Problem Solver

Re: Router(s) fail to connect to cable modem

Did you powercycle the modem? Anytime you change the device directly connected to the modem, you have to powercycle the modem.

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New Poster

Re: Router(s) fail to connect to cable modem

I did, multiple times. No dice.

Re-connect to computer, power cycle Modem, computer connects.

Re-connect to router, power cycle Modem, router shows "No WAN connection"

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Diamond Problem Solver

Re: Router(s) fail to connect to cable modem

Maybe time to troubleshoot through Arris support?

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Expert

Re: Router(s) fail to connect to cable modem

@gnida_rada 

 

As a work-around, if the router of your choice has a MAC address cloning feature, you could try cloning the MAC address of the computer that works into it. This will trick the modem into thinking that the computer is directly connected to it (no router present). Don't forget to power-cycle the modem if and when you try that. Good luck !




I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
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New Poster

Re: Router(s) fail to connect to cable modem

It was working just fine for over a year. Then stopped. I bought new modem. Same issue. 

Considering that the old and new modems showed the same symptoms, I doubt this is Arris.

In any case, 16 hours later it all started working ,on all modems and routers I have. Which again confirms to me this has someting to do with Xfinity

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Silver Problem Solver

Re: Router(s) fail to connect to cable modem

As well as trying EG's good advice, try starting from scratch.

Connect everything as you want it, modem/router/computer.

Power them all down, then connect modem give it time to come up, then router, then computer.

If that fails, try factory resetting the router and rinse and repeat.

Can't see it being an Xfinity problem if you get a connection on the computer.

 

(missed your last sentence, glad you got there. I'll leave this here).

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New Poster

Re: Router(s) fail to connect to cable modem

This started happening to me in the past month too. Also have an Arris Surfboard, model 6141 cable modem. I figured out that when another device was connected to the network (mobile phones, computers, etc.), for some reason it would steal the role of the router after rebooting the cable modem. I could tell by looking at the support page of the cable modem: under the Addresses tab, in the "Known CPE MAC Address (Max 1)" field, it would show the MAC address of some random device, like a mobile phone or computer.

 

To fix this, I connected to the router with a laptop via a wired connection, disabled the wireless functions of my router via the admin page, unplugged the Chromecast from the TV (yes, I HAD to do this, as it was not only seeing the wireless network, it could also see the cable modem wired through the TV), disconnect the laptop, powerdown the router and modem, and the power up the modem, and finally the router. Once the router successfully connected to the modem, I connected the laptop to the router and reenabled wireless functions ,and finally plug the Chromecast back in. Sure is a pain to have to do this every time the network goes down and comes back up. I wonder what changed.