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How to turn Bridge Mode on and off on Xfinity modem
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This article provides information on how to complete your XFINITY Wireless Gateway Self Install and Activation
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  This article outlines how to activate your Xfinity Internet/Xfinity Voice service if you rent an Xfinity xFi Gateway (Arris 1682G, Cisco 3941T, Arris 3482G, Technicolor CGM4140COM or Cisco DPC3939). To determine the type of Gateway you have, check the make and model information located on the bottom of your device. You can also log in to  My Account  and select  Devices  to view the make and model of your Gateway.   If you do not have an xFi-compatible Gateway, please see the activation instructions for other Wireless Gateway devices.     Activation Instructions Before you start: Download the Xfinity xFi app for free from the Apple App Store or Google Play. Launch the Xfinity xFi app and sign in using your Xfinity username and password. (You must be the primary or an unrestricted secondary user to access.) Select   I'm setting up my Wireless Gateway. After activation you can continue to use the Xfinity xFi app to manage your home network. Select   Get Started   to begin the process of setting up your Gateway. The entire process should not take longer than 20 minutes.   Select   Use Camera   to scan the QR code on the side or back of the device. The QR code should contain all of the information needed to begin activation. You may also be prompted to grant the Xfinity xFi app permission to access your smartphone's camera.   Note:   If your device does not have a QR code to scan, you will need to enter the 12-digit CM MAC number found on the side or back of the Gateway. Select   Enter Code Manually   and follow the on-screen prompts. You may also be prompted to enter the CM MAC number even if your device has a QR code if we need additional information. Your smartphone's camera will open within the Xfinity xFi app. Find the QR code and focus the camera on it. Once the QR code has been successfully scanned, you will see a green check mark. Note:   Keep your smartphone as steady as possible. If the camera has trouble focusing on the QR code, try slowly moving your smartphone away from and towards the QR code. The app will then take you through the necessary steps to set up your Gateway (modem/router) and activate your Xfinity Internet/Xfinity Voice service. For the best WiFi coverage, set up the device in the most centrally located place in your home where there is also a cable outlet. Also, avoid placing the device in your basement or attic as this can interfere with your WiFi signal. Keep it out of cabinets or closets, and make sure it is off of the floor. Select   Next   to proceed through these tips. Once you've found the best spot for your Gateway, follow the instructions to connect the coaxial cable and power cord. The lights on the front of your Gateway will flash and blink as the device prepares for activation. Select   Ready to Go!   to continue.   Now that your Gateway is connected, it's time to personalize your home WiFi network name and password. Enter a WiFi name and password that is easy to remember and secure. Select   Next. Confirm the WiFi name and password you entered are correct. If you need to make changes, simply select the back arrow in the top left-hand corner of the screen. If you are also activating Xfinity Voice, you will see your phone number on this screen. Select   Confirm and Finish Up. Note:   For customers swapping an existing xFi Gateway with a new one, you may be presented with the WiFi name and password associated with your previous device. You can choose to keep them the same, or create a new WiFi name and password. If you change the name/password, you'll need to reconnect all your devices using the new information. Your home network setup will now begin. This can take up to 10 minutes to complete. You will also be prompted to enable push notifications to be alerted when activation is complete. Once your Gateway is activated and your WiFi is ready to go, you'll be presented with instructions on how to connect to your new WiFi network. Two shortcuts are provided to make this process even easier. Simply copy your WiFi password to your clipboard by selecting   Copy   and then   Go to Settings. From there, go to the WiFi settings on your device, wait for your new WiFi name to show in the list of available networks, join the network and then paste your password to connect. Remember, you'll need to connect all of your WiFi-enabled devices using the WiFi name and password you created. Select   Continue to XFINITY xFi   to access home network personalization and control features, for example the ability to see who's most active on your network, troubleshoot any connection issues, and block inappropriate content and network threats. To learn more about xFi features, see the   overview for Xfinity xFi Web Portal and Mobile App.
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How to find a compatible modem with your Xfinity Internet service
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 I have no Internet access and  the US and DS buttons on the modem are blinking. How do I solve this?
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    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 v isit 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.cm 5) Verify that you have 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 available 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 have 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 leave 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 have 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.  
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In order to keep your Wifi network secure you may need to change your Xfinity Wifi password. Here are a couple of different ways to get that completed. 
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How do I log into my XFINITY modem so I can manage my home network?
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This article will explain what port forwarding is and how to use it on your in-home network. 
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We see many questions in the forums regarding port forwarding, so I have put together a primer to try to help those who are new to the concept.   WARNING: Port Forwarding exposes devices on your LAN to the Internet. If you DO NOT NEED to port forward, DON'T. This guide tells you how to and why you might need to port forward. The reader assumes any and all responsibility for any damage of, or intrusions into their network caused by port forwarding. What is Port Forwarding? Port forwarding is a mechanism used in IPv4 to allow a computer, smartphone, or other device (the SOURCE) outside your Comcast HSI connection to connect to a device on your LAN (the DESTINATION). A typical Comcast residential user network might look something like this: In this diagram, a Cable subscriber (you) has a webcam, NAS, or media server on the internal LAN behind his router/gateway. It is configured to listen on TCP port 8080, in this case. Other devices or game servers that you have may be configured to listen on a different (or many different) ports, but the principle is the same. Let's say that the subscriber (you) want to make that server available to a family member in a different location, so they can see your webcam, or look at pictures on your media server or NAS. In order to do that, your family member needs to be able to connect, often using a web browser, or a smartphone app. The problem is that your web server is on your LAN, protected by the firewall in your router, AND it has a private address, which cannot be used on the internet. The private subnets you will see most commonly are the 192.168.0.0 and 10.0.0.0 subnets. Subnetting is beyond the scope of this discussion, as most home routers are set up out-of-the-box to use one of these submets. Under normal circumstances, you will probably never have to change this. The problem lies in the fact that these subnets cannot be routed over the internet. Port Forwarding is intended to solve that problem.   As seen in the diagram, your home router (and you must have a router of some type to perform port forwarding) is provided with an address on the public internet by Comcast. Because of a shortage of IPv4 addresses, home routers use Network Address Translation (NAT) to allow you to connect a large number of devices to your router, and give them the ability to connect to other devices on the internet. This is done by assigning each requested connection from your LAN a TCP port, so the router can track the connection. The combination of the IP address and port number is called a socket. So, when you use your computer on your LAN to go to www.google.com, your computer (the source) sends a request using a random port (usually above port 1024) to the destination (www.google.com) on port 80 (the standard http port. Because of NAT, the Google server sees your source address as the WAN IP of your router. How, you may ask. is this related to Port Forwarding? Well, port forwarding is essentially the same process, but in reverse. Think of it as inbound NAT. You router has a public IP address, but by default, it doesn't listen on many ports. This is for security, so that someone on the internet cannot easily get on to your network. Now, you have a media server or an IP Camera that you want Granny to see, so you have to tell your router to listen on a port so that you can give Granny a link to it that she can put in her web browser (how she does that we will discuss later).   How do I set up Port Forwarding   First, you have to set up your router. There is an excellent website at http://portforward.com, which will walk you through the steps of how to forward ports on just about every known router, so I am not going to go into detail on any particular model. Suffice to say that when you set up port forwarding, you tell your router to listen on a particular port (in the case of the diagram, it is port 8080), and you also tell it where to send that traffic, when it sees it. In this case, the router is told to send all traffic it ses incoming on port 8080 to the internal device at 192.168.1.200. Below is an example of the screen for configuring a Custom port forwarding service on a Netgear WNDR3700. Other router screens will look different. This is just one example:   OK, so I have set it up...how does Granny get there... Granny has a computer with a web browser. Lets say you are letting her see your IP Camera. instead of port 80, your IP Camera is designed to listen on port 8080. Under normal circumstances, you would forward the same port externally as the device listens on, so you would set up your port forwarding to listen on the WAN interface on port 8080, and internally, send all port 8080 traffic to the IP address of your IP camera. Now, when Granny browses google.com, she just types inwww.google.com in her browser, and it goes there, right? That is because google.com is listening on a well-known port for http traffic (port 80), and browsers automatically know that you want to go to port 80. What they don't know is that your router is waiting to send traffic to your IP Camera on port 8080, so when you tell Granny how to get to your camera, if you are using any port other that 80, you MUST specify the port, and that you are using the http protocol. So, you would tell granny to put the following in her browser address bar: http://<yourWANIP>:8080   To find the WAN IP of your router, you can either look at the Status page in your router interface, or browse tohttp://whatismyip.com If you don't want to give her an IP address, you would need to use some type of Dynamic DNS service (not within the scope of this discussion) to translate your WAN IP into a hostname, but you still need to specify http and the port number, like this: http://myipcam.somedomain.org:2000 (the actual name will depend on your Dynamic DNS provider) What else can I do with Port Forwarding?   The principles are the same for pretty much any device or server that you want to make available to sources outside your home. You can port forward Windows Remote Desktop Protocol, so you can log into your PC from another device with an RDP client. You can run a web server (although publicly accessible webservers are technically against the Comcast AUP for residential connections), you can access your own media server from your smartphone, so you can listen to your music wherever you are...the possibilities are pretty much endless, BUT make sure that you secure the devices you are allowing access to with strong passwords. While many security experts frown upon the concept of 'Security by Obscurity' I personally don't see that it hurts to change the port you are using for some services, especially the more common ones...Any hacker knows that Windows Remote Desktop Protocol runs on port 3389, so instead of setting your port forwarding up to listen on port 3389 on the WAN IP, use a different port (above 1024 is recommended. The highest you can go is 65535). You can still tell the router to forward the traffic to port 3389, so you don't have to mess around with the registry settings for your RDP setup on your Windows machine. That is basic port forwarding in brief. If you have any questions, please post it in the forums in the Home Networking / Router / & WiFi Gateway Help board and we will try to help. Be aware that as of writing this (April 2013) there appear to be some issues with port forwarding on some of the Comcast supplied gateway devices. Unfortunately, there isn't much we can do to remedy those, if you have set up port forwarding properly. The suggested solution is to have the gateway placed in bridge mode, and buy your own router to do your port forwarding. Also there are some quirks to setting up port forwarding on the SBG6580 gateway. See this post for details: http://forums.comcast.com/t5/Home-Networking-Router-WiFi/Port-Forwarding-for-an-IP-Camera/m-p/152957... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Learn about what a home network is and why you need one.
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This article provides detailed information about Comcast provided Wireless Gateways and their features. 
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