Upgrading to gig speed with a different non Xfinity cable modem

Hello Miltonpyron. Thank you for visiting and posting on our Forum. Apologies for our delay in getting to your post. I can assist with the activation of your internet service. Please send me a private message and include your full name so I can access your equipment.

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@Miltonpyron wrote:

SB8200 modem, internet works fine with my original Arris modem. I upgrade online, received a self install kit, which consisted of the Xfinity Flex device and nothing about activation of modem.

I followed all the instructions from Xfinity online to install. Ethernet from modem to iMac.

I get error not connected to Internet. So apparently it needs to me activated by Xfinity.  Automated system is useless, circular and repeating everything I already did and never has prompt to get to a person. What the heck?

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I realize this post is a bit dated, but you can't use both the ethernet ports on the SB8200. Only one is active at a time. You need a router to connect more than one device to your modem.