Internet access limited to a single device after activation with Xfinity.
Internet access limited to a single device after activation with Xfinity.
Hello! I recently purchased two modems: an Arris Surboard SB8200 and a Netgear CM1000. I went through the activation steps for both using the automated system with the CM1000, but after that, the device became unresponsive. I then activated it manually on the Arris SB8200. The problem is that the internet only functions on the modem used to activate the Xfinity service. When I called support, they mentioned a reset signal and tried activating it on another computer, but the issue persisted—only that specific device worked. It doesn’t work on any other computer either. Game consoles, Wi-Fi routers, or other devices are unaffected. It seems the issue is tied to the Xfinity activation process itself. Have others experienced similar problems?
I’m assuming you’ve started by turning on the modem, then the router, and finally your computer. I know Xfinity assigns IP addresses using DHCP based on the device’s MAC address. That means the modem would need to restart and the whole DHCP setup would have to reset so a new IP could be issued for the router. Another method you could try is cloning the MAC address of the device that activated the service. If your router supports this, it might work, though it shouldn’t be required.
I started the modem, waited for it to connect, then connected an Ethernet cable from the modem to my router. After powering it on, it still didn’t receive an internet signal. I checked from my desktop to confirm and found no internet connection. Even when connecting directly to my Nintendo Switch via the modem, it also showed no internet access despite being plugged into an Ethernet port.
I reached out to Arris and they guided me through a reset process: cut power, hold reset for half a minute, connect coaxial, wait for stabilization, then link Ethernet to another machine. Only that specific device now functions. When I tried it on my MSI laptop, the network appears unrecognized and no internet access is available. I’m puzzled—despite knowing DHCP is set, the modem seems stuck in default mode. The interface lacks options beyond basic settings, and even the advanced settings only let me enable a limited feature called "LAG" for pairing. It looks like resetting the modem and connecting one device is what’s actually working.
That's because on the modem those are not settings you need to worry about. The modem will connect whatever the ISP requires. Comcast provides both firmware and configuration updates regularly, but only the ISP can push updates for cable modems. The LAG function is used when you need more than 1 Gbps, and some cable modems have multiple ports. Connecting all ports to the same router might help achieve faster speeds, though most ISPs still cap coaxial connections at around 1 Gbps. The only steps you should take are restarting the modem after adding a new device. Otherwise, nothing else is necessary. You could also try resetting the modem and testing with the router as the sole device. If that doesn't work, consider returning the modem or trying a different one.
Alright, I just tested my older Arris modem. I’ve used it with two different Xfinity accounts at two separate locations—one of which includes this one—and everything is working perfectly. Before setting it up, there were no issues plugging it in, and all devices on my network connected instantly. Now I have three different modems, models, and brands. When I log into my Xfinity account online, it reports an internet problem and directs me to customer service. It seems like the issue is likely on Xfinity’s side. With someone having less than three years of experience, they probably haven’t heard of it and just say they’ve never encountered it. No offense to anyone I’ve spoken to, but when something isn’t working, it’s usually better to send the customer to a more experienced team member instead of just wishing them luck. Thanks for trying Donut! If you hear anything, please let me know. Appreciate your help!
Just to clarify, switching the device connected to the modem (like your router, PC, or console) isn't necessarily power cycling the modem. Most Cable ISPs use a CMTS chassis that assigns an IP address based on the first device plugged in, not the one you change. If you connect a new device via Ethernet without rebooting the modem, it might not receive an IP address from the updated setup.
Not sure you know how CSR's work. Comcast expect them to sell you more services, even though the current services dont work. Comcast is known to have some of the shittiest customer service in the industry. https://www.dslreports.com If you sign up for an account, you should see ISP Direct to members support section on the right side, just scroll down. Comcast has technical support forum on this site. Its staffed by the guys out of Philly, the Comcast HQ, not the local idiots you have been talking to. Ive heard they have been getting swamped with requests, but make a post. Explain to them what's going on. You might get more action from them.
Haha, I get it. I’ve been in that role for 4-5 years handling installations and repairs, working on projects like U-Verse, Fairepointe, Alta, Linx—though Linx isn’t relevant here since they do heavy cable pulling. At AT&T, we usually escalate issues instead of pushing for better gear. But this one really confuses me because I’ve never faced it before. I’ve used the standard setup without any complications, and even at my house it worked fine. Sorry if I’m repeating things.