Very slow internet speeds --for several years

(1) WIrelessly. (None of our computers have ethernet ports, so a direct connection is not possible.)

(2) Same result on all devices.

I appreciate the additional information, @user_4yzvrv. Let's take a look at the account. Our system will determine if we need to send a technician over to investigate. Could you please send our team a Direct Message with your name and service address? We can take a further look at this issue.

To send a Direct Message:

Click "Sign In" if necessary

• Click the "Direct Messaging chat" icon

• Click the "New message" (pencil and paper) icon

• Type "Xfinity Support" in the "To:" line and select "Xfinity Support" from the drop-down list which appears. The "Xfinity Support" graphic replaces the "To:" line

• Type your message in the text area near the bottom of the window

• Press Enter to send it

I already sent a DM to Xfinity support. Are you looking into my account?

We are happy to help and appreciate that you sent the message, @user_4yzvrv. I am replying to you there now. I need to gather your account details to take a deeper look into this. 

(1) Yes, all devices are capable of in excess of 1000 mbps. My Asus laptop, for instance, can handle over 1300 mbps.
(2) We notice the slow speed when loading pages from all websites. We don't play games and I am not aware of any random disconnections at all. The internet remains connected almost all of the time.

(3) I followed all of the "Tips to Improve your Wi-Fi speed" and performed another speed test. The download speed was still very slow at 300 mbps --far less than I am paying for.

Thank you for providing this info. 

How/where do I make the DNS configuration changes you list above? Do I have to log into my Netgear modem-router and make the changes? Or do I do it through the browser (e.g. Chrome) I'm using on my laptop? Or what?

Please note that I have an Asus laptop. The other devices are an Acer Chromebook and two Samsung phones.

Specifically where do I put insert these DNS numbers? 

192.168.0.1

75.75.75.75

8.8.8.8

162.150.8.51

It's so nice to meet you, @user_4yzvrv ! How is your day going? Thank you for sending your information so I could locate your account. In order to review account details, I'll need to send a security code to the primary Email address or phone number on file. Which option works better for you? 

Phone number  please

@user_4yzvrv​ 

Specifically where do I put insert these DNS numbers? 

192.168.0.1

75.75.75.75

8.8.8.8

162.150.8.51

Answering to your question, you will using these DNS numbers both on your computer and Modem/router.

- What model of computer do you have? Mac, Windows?

I could give you the right information if I had more information about your router and computer model. The only thing you told us is the model of your router.

Both computer and router has DNS configurations, and both computers and routers use private intranet IP addresses.

You have to find out what kind of the subnet/intranet your Netgear Modem Router is assigned to! Subnets are basically divided in A, B and C.

The private IP addresses that you can assign for a private network can be from the following three blocks of the IP address space:

• 10.0.0.1 to 10.255.255.255: Provides a single Class A network of addresses
• 172.16.0.1 to 172.31.255.254: Provides 16 contiguous Class B network addresses
• 192.168.0.1 to 192.168.255.254: Provides up to 216 Class C network addresses

If your router is assigned to the Class A, 10.0.0.1, that will be your intranet DNS.

If your router is assigned to the Class B, 172.16.0.1, that will be your intranet DNS.

If your router is assigned to the Class C, 192.168.0.1, that will be your intranet DNS.

Your Netgear Router/Modem gives you 3 fields to enter DNS numbers.

You must log into your Netgear Router and navigate to ADVANCED > ADVANCED Home > Internet Setup

On the Field called "Domain Name Server (DNS) Address.

Select:

(O) Use These DNS Servers

There you can enter the 3 DNS numbers of your choice. In my case, I entered as a

Primary DNS       75.75.75.75

Secondary DNS 162.150.8.51

Tertiary DNS       9.9.9.9

The most important is the Primary and Secondary DNS. The third one is extra. You can enter the 9.9.9.9 or 8.8.8.8. Both will work very well. Look the example of the image bellow.

After you have entered these DNS on your Netgear Modem/Router, you click on "Apply" to save your DNS configuration. These are the DNS you will be using on your devices in addition to your intranet A, B, C DNS.

In my case, these are the speeds I am getting on my Modem/Router

Two tests, from different servers xFinity always show a little bit more on speed.

Not bad for an outdated Netgear router! Next week I will be testing a new 3.1 Modem router able to deliver 951Mbps. So will be interesting to see how that will work.

Thank you so much. I'm going to drop speed tiers and save some money. I figured that this might be the best move.

@user_4yzvrv​  As far as expected/theoretical WiFi bandwidth goes, your Netgear speaks these standards:

Data encoding standards IEEE 802.11ac 2.0
IEEE 802.11n version 2.0
IEEE 802.11n 256QAM IEEE 802.11g, IEEE 802.11b 2.4 GHz 
IEEE 802.11n, IEEE 802.11a 5.0 GHz

Now, for 802.11b connections, you might only see 11Mbps of throughput.  802.11n might get you up to 600Mbps, but likely won't be that fast.  802.11ac can theoretically do 1.3Ghz of throughput, but you'd rarely see that.  This would also be device to LAN device, and not device to the world/internet.  That's a lot to benchmarking that, and it depends on what you are using for a WiFi device, and the radio chipset it uses plus the software stack it's running.

If you are getting from 30-80Mbps on a device over WiFi?  Well, it's plenty fast enough to stream a full 8K movie.  Bandwidth you actually have to test with something other than WiFi to see what you're getting to Xfinity and through their data center to someone else.  

For reference if you can't find the DNS settings (or I gave you a bad place to look), or the firmware changed from a normal Netgear along the way, here's what they got for a current manual for it:  https://www.downloads.netgear.com/files/GDC/C6900/C6900_All_MSOs_UM_EN.pdf 

*I should probably also add:  The speed tier you select?  That's the "UpTo Speed" all of your devices pulling data at the same time, so if you got a couple of users, keep it in mind.  You can max out bandwidth with a few users, and a low speed tier depending on what you are doing.  

@flatlander3​ What do you think might be causing pages to load slowly? It's the slow-loading pages that made us think the internet connection was slow. 

@user_4yzvrv​ DNS lookups can be part of it.  I've never had good luck with comcast DNS and use other ones.  Look at all the trackers that load on this page alone.  It contacts 40+ unique addresses that flash by on the bottom of your browser if it shows you thim if you don't control it with a script blocker.  That's common everywhere.  

Scripts and multi-media content that makes up web sites these days are an issue.  Tracking cookies.  Browser hijacks.  Maulware you may have picked up.  Try clearing your browsers web cache and cookies.  Use an anti-virus scanner with a "boot time scan" to pick up stuff it can't see after the OS loads.  Windows installs have bloatware issues that degrade performance all by itself.  Keep all your software updated, including the OS.  Make a backup of your data, and try resetting it to default, or reinstalling windows if that's the issue.  

If you want to see a difference, try an Ubuntu linux DVD or memstick and boot from that.  There's a tutorial on the download page (ubuntu.com) Don't install it, just run from memory and see if your OS is the bottleneck.   

If you want check for signal issues, log into your netgear and look at the signal stats/errors there.  They're caused by a lot of things, but your own household wiring/splitters/connectors/amps (if you have them) can cause issues.  It's a good place to look  Here's a troubleshooting guide on what to look for:  https://forums.xfinity.com/conversations/your-home-network/internet-troubleshooting-tips/602dae4ac5375f08cde52ea0 

Downstream power should be from -7dBmV to +7dBmV.  SNR should be up over 38 or higher.  Upstream channel power shouldn't be higher than 50dBmV on your netgear.  Mine flakes out if it goes over that.  All channel power should be within a dBmV or so at all frequencies, otherwise, there may be some component like a splitter causing issues. 

There's no one cause.  It could be many at the same time or a neighborhood infrastructure issue too.