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I just got connected to xfinity internet today with my new SB6183. When I directly connect my computer to the modem, I connect to the internet just fine. When I connect the modem to my wifi router, nothing. Do I need to update any settings in the modem prior to connecting my router? Or is this just a router issue? The router was working just fine 10 min ago connected to my old modem.

The modem only gets 1 public ip address. If it was assigned to the computer it can take a bit to be assigned to the router. Disconnect the computer from the modem and power it off for 10 minutes. 

Then power it back on and connect the router to it (with router off). Then power the router on and go through its internet setup process. 

Most ISP’s reassign the ip address in a minute or 2 but waiting 10 should clear it. In rare instances I’ve heard of it taking up to 30 minutes


Thanks so much for your help! It’s crazy how simple some of the fixes can be…. Is it plugged in, did you turn it off and back on?

waiting the full 10minutes fixed it. All good now!


plemans, I want to thank you for the clear explanation. It helped me immediately solve my issue.

For days, I was pulling out my hair and raging at both the ISP and multiple router manufacturers because no one could figure anything out!

I was forced by Comcast to buy a new DOCSIS modem and must have plugged my PC into it to configure settings. Then once I connected my old router, it reported no internet connection.

Then days of contacting various tech support and buying new routers followed -- all to no avail. One Linksys “expert” even suggested my low speed ISP plan was causing the router problems!

But your expert insight confirmed my own observations and suspicions and gave me clear steps to fix things. LUCKILY, I found your post on this website and it restored sanity and order in my home.

THANK YOU, THANK YOU, THANK YOU!!!