1) Directly connect to your modem via ethernet.
Restart your modem everytime you plug in a new device. It's a good time to replace your Ethernet cables; Cat6 preferred. If your speeds are good, concentrate on router/networking issues. If the speeds are still poor, concentrate on modem/signal issues. Do not test speeds over WiFi.2) Test your speeds on Xfinity's network.
Use http://speedtest.xfinity.com/ as your primary speed test. This means you'll be testing on Xfinity's network exclusively. This eliminates routing or internet congestion as potential problem sources.3) Verify that your modem is approved for gigabit speeds
See Approved Xfinity modems and gateways. Or My Device Info.4) Verify that your modem is provisioned for gigabit speeds.
To find your speed tier visit My Device Info. After you log into your account, your speed tier will be displayed on the left-hand side of your screen. Alternatively, you can view the speed tier to which you are subscribed here. Sign in and scroll down to the data usage graph area. If your modem displays a bootfile it should look something like this: d11_m_xxx_gigabit_c01.cm5) Verify that you he 10/100/1000 (Gigabit) network adapters.
No USB adapters. Verify that the adapter is set for Gigabit speeds, full duplex.6) Verify that you meet the minimum system requirements.
Xfinity Internet Minimum System Requirements - For Speeds up to 1 Gigabit per second Operating System Windows 10 (64 bit) or newer or Mac OSX 10.8 or newer. Visit the Microsoft Windows lifecycle fact sheet or Mac OS X Support overview for their latest operating system information. Browser Google Chrome 56.0.2924, Microsoft Edge (64-bit), Mozilla Firefox 52 (64-bit) or Safari 8 or newer. For more information about different browsers or to download a new one, visit whatbrowser.org. Ethernet Cable Cat5e or Cat6 Ethernet cable.Note: Due to Ethernet overhead, actual download speeds are limited to 940 Mbps over a hardwired connection. Ethernet 10/100/1000 Gigabit Ethernet interface or adapter for wired connection CPU/Processor Intel Dual Core i5 or better or AMD Ryzen 5 or better Memory 8 GB of RAM minimum Hard Drive / Space 64 GB or larger SSD recommended to achieve maximum download speeds
7) Make sure your signal levels meet specifications.
See the troubleshooting guide. And/or watch a how-to video. The video is also ailable at the bottom of this post. 8 ) Turn off security software briefly and test speeds.
Antivirus and malware software can significantly impact speeds if they are too restrictive. Do not run multiple antivirus programs. Your operating system may also he overly restrictive security settings.9) Boot into safe mode with networking and test speeds.
If your speeds are good, concentrate on software issues. If your speeds are poor, concentrate on hardware issues. For Windows 10: Restart your PC. When you get to the sign-in screen, hold the Shift key down while you select Power > Restart. After your PC restarts to the Choose an option screen, select Troubleshoot > Advanced options > Startup Settings > Restart. After your PC restarts, you'll see a list of options. Select 5 or F5 for Safe Mode with Networking. To load your Mac in Safe Mode (aka Safe Boot), press and hold the Shift key while it boots. You can stop holding the Shift key when you see an Apple logo and progress bar. To lee Safe Mode, just reboot your Mac.10) Ask for help on the forums.
The community will often be able to offer you sage advice. An employee can check your modem/node health and review current and historical reports related to your modem. 11) Request a tech visit.
If all else fails, schedule a tech visit. Techs he specialized testing equipment such as the XMT, an ODROID-based device designed specifically to test speeds. They can determine definitively if it's an Xfinity issue or a wiring/home networking issue.
Additional Resourceshttps://forums.xfinity.com/t5/Internet/ANSWERED-Tips-for-troubleshooting-your-Xfinity-Internet/ta-p/2941127
https://forums.xfinity.com/t5/Internet/ANSWERED-Troubleshooting-your-XFINITY-Internet-connection/ta-p/2941135
https://www.xfinity.com/support/articles/xfinity-home-network-guide-troubleshooting
https://www.xfinity.com/support/articles/check-xfinity-outage-map