Hi MBrennan,

May I know the model number of your device? 

It is Arris SB8200. I just figured out that it does not have a valid IP address. How do I set that up? Everything has been done with comcast and is ready to go

Hi MBrennan,

SB8200 is a cable modem, and a router needs to be connected to it in order to access the Wi-Fi.

If the device is activated by the service provider, no specific setup is required.

Please complete the power cycle in the following sequence:

1. Disconnect all the cables from the back of your modem.

2. Wait a minute or two.

3. Reconnect the coaxial cable.

4. Reconnect the power cable.

Once the lights are solid, you can connect your computer to the modem to check for a public IP.

Hope this helps!

I do have a router connected and I have done all the items you suggested. My Wi-Fi is still not coming up on the list to be available. I plug my Comcast modem back in and works fine???

Hi MBrennan,

Here are my suggestions.

1. Reconnect the SB8200 and check your Xfinity app to see if the SB8200 modem is online or offline.

If it shows offline, the modem has to be re-provisioned by the service provider.

2. If it shows online, please connect a computer directly to your modem (after a complete power cycle) and check for Internet access and IP address. so that we can isolate the issue. 

I confirmed the device is activated properly and I did hook my laptop up to the Ethernet port but it keeps coming up as the IP address has not been established 

You should only use 1 Eth port on the SB8200 since it’s just a cable modem and does not have Wi-Fi capability.    
 

It’s hard to see the SB8200 causing you not to see your router’s Wi-Fi.  You should see the Wi-Fi even when the router is not connected to a modem.  

When coax cable is connected to SB8200, the device connected to SB8200 gets an IP from your Xfinity.  When coax is disconnected, the device would get 192.168.100.x from SB8200.

Based on my experience, it could take a few hours to get Internet after activating a new service. 

Thanks for the feedback. After a long day of tech support it ended up being a bad router. I never knew the xfinity modem had a built in router because when they connected it years ago they plugged my external router into it. Not being a very tech savvy guy I just assumed that when I tried the new modem and couldn’t see the router that there was a problem with the new modem. Anyway, going shopping for a new router for my arris SB8200. Any suggestions?

I had a feeling that Xfinity device could’ve been a wi-if modem combo. I don’t blame you, networking equipments are really confusing. 
 

I recommend mesh routers (for >1200 sq ft home) with at least wi-if ax capability.   I have ARRIS W121 Mesh System in a 1500 sq ft home. 

Thank you!

Mine is working just fine with an Eero mesh system, but the data rate is significantly diminished from the rate coming out of this modem.