Hello, and thank you for reaching out for help with your service. I rely on a speedy connection, for everything from work to entertainment, so I can appreciate the need to ensure your serivce is working as intended. 

Because outdated equipment and firmware can slow down what would otherwise be a fast connection, you'll want to make sure your network setup is always up-to-date to get the most out of your Xfinity Internet service.

Like computers and mobile devices, new WiFi equipment models are released regularly. While you don't need to immediately update your equipment to keep your home network running, you could be missing out on improved services if you continue to use older models. I can take a look and see if you would benefit from a new device. It sounds like the model you own is a DOCSIS 3.0, and for 800/35 Mbps, recommends DOCSIS 3.1 or higher devices. @TN_Knox_User, have you tried upgrading the equipment as a test yet? 

I just upgraded my equipment to one that was recommended by the Xfinity website to support 800Mbps.  My equipment is not outdated, but my firmware is.  It's xfinity's responsibility to keep the firmware current, not the modem OEM.  I could go out and spend $200 on a new DOCSIS 3.1 modem and experience the same problem because xfinity fails to support the devices that they recommend yet fail to support in the field.  The customer is the one that pays the price for xfinity's inability to manage their device infrastructure.

@XfinityJohnG wrote: "... It’s important to remember that we can’t as easily update the firmware ... if you’re using equipment other than one of our Gateways. ..."

This statement is incorrect. As the OP has stated and as any manufacturer website will state, if modem or gateway firmware updates are required they are supposed to be applied by, and can ONLY be applied by, the ISP. This typically happens automatically whenever a modem or gateway connects to their network.

Please be aware that there are 2 kinds of responses in this Forum: Replies and Comments. When you Comment on a post by scrolling down to "Comment on this post here...", I am notified of your response. But if you select Reply, I am NOT notified and may not be aware of your response.

Hello XfinitySelena:

Thanks for your response.  Sure I'll DM you.  However, let me give you some detail as to some of the troubleshooting that's already been done.

1) I was having intermittent network dropouts during the Summer of 2022.  On the second visit by a tech to my house on 9/9/2022 for this issue he replaced the cable from the pole to the house and since then the drop outs have stopped.  He measured the speed from the pole and it was multiple Gbps download speed and the signal strengths were great.  I consider this issue resolved.

2) During September 2022 I received an email from xfinity saying that my cable modem couldn't keep up with the network speeds of my service.  At that time I had 600Mbps service and was using a Netgear CM500 modem.  The speedtest measured speeds were almost 500Mbps.  I was satisfied with the speed and did nothing with regard to the email.

3) During late October 2022 I received another email from xfinity saying that they would be increasing my service speed to 800Mbps by the end of October 2022 requiring me to restart my modem.

4) During late October 2022 I received one more email from xfinity stating that my cable modem couldn't keep up with the network speeds of my service.  I assumed this was do to the increase of service speed to 800Mbps.  I responded to this email by going to the Xfinity "Device Info" website and selected devices with a 800Mbps download speed.  From the approved list of devices I selected the Netgear CM700 which was certified, per the Netgear CM700 datasheet, by xfinity for 800Mbps service.  Now with the upgraded service and device my speeds are 400Mbps which is less than what I experienced with the 600Mbps service and the CM500.

5) Over the last week I've spent over 2 1/2 hours on the phone with your support staff and the support staff supervisor troubleshooting the slow data rate issue.  In both cases they told me that I needed to upgrade the firmware in my modem to get the faster speeds, but that they weren't able to do it.  They said Netgear has to do it.  I knew from reading the Netgear website that this recommendation was wrong.  But, I contacted Netgear to double check and they said that they weren't able to update the firmware and that I'd have to have xfinity do it.

So, this leads me to my current situation where my CM700 needs to have its firmware updated from V1.02.02 to V1.02.08 to handle the 800Mbps service, but neither xfinity or Netgear is able to upgrade my device.

Best regards!

I followed XfinitySelena's advice and DM'd their support people.  They essentially provided the same support function as is done via phone.  After running their tests I was told that there was a problem with my connection to their network and they recommended a technician come out to investigate the situation.  I seriously doubt this is the problem.  Just another rabbit trail. ... It's seems like we're back to square one again.  Please read the previous post about why I don't think the problem is my hardwired connection.

I just received an automated message from xfinity saying that a problem was found and resolved, and that I no longer needed my technician appointment.  I restarted my modem and did a speed test and the problem still persists.  Errors still occur in the event log after restart.  This shouldn't occur.

The one bit of information that xfinity keeps ignoring are the errors in the event log.  It indicates that the modem isn't being provisioned properly.  Here's what's supposed to occur via Cable Labs.

How to provision a cable modem using the ISC DHCP server

It appears the problem is that during this DHCP transaction, which occurs when the modem is powered on, that even though the configuration file name is provided the IP address of the TFTP server is wrong.  Since it's wrong the modem can't access the named configuration file which defines the network speeds, firmware versions, etc. and by default uses the default parameters found in the modem.  It seems that xfinity should have a network engineer that could look at the provisioning information for my modem to see if indeed this is the problem.  This should be a very simple item to check if the correct person could be engaged!

This problem still persists and xfinity continues to ignore the problem they have with supporting their customers issues in the field.  There should be a very simple and straight forward solution to the problem I'm having.  I'm a very disappointed xfinity customer whose service issues are being ignored!!

Having this exact same issue, with this exact same equipment. My issue is worse, though: I am paying for 800mbps, but only getting 150:

@TN_Knox_User have you tried reaching out by Reddit, Twitter and other social media? Support seems to ignore all channels.

No.  I haven't tried reaching out via social media.  I've only contacted xfinity by phone and direct messaging.  The last contact via DM suggested a technician come out to evaluate the situation.  He came out this past Saturday morning.  The first thing he said was that I needed a DOCSIS 3.1 modem to get the 800Mbps speeds.  I told him that I bought the CM700 via recommendation from the xfinity Device Info website.  He said that he doesn't know why they recommend anything except DOCSIS 3.1 modems because anything else won't get the faster download speeds.  He said the only modems that xfinity rents in my area are the Motorola and Arris DOCSIS 3.1 modems.  He measured my download speeds with his test device at 1.8Gbps.  So, my cable connection is good.  I asked him why my modem wasn't provisioned properly.  He said it was, but that couldn't be true.  His final words were that my "new" modem was probably bad and that if I wanted to get the faster download speeds I should buy a DOCSIS 3.1 modem.  He also said that xfinity is updating their infrastructure in my area to get faster download and upload speeds and that is another reason to buy the DOCSIS 3.1 modem.  The technician was very friendly and gave some good information.  It's just very frustrating that xfinity continues to recommend modems other than DOCSIS 3.1 when the real world experience of their technicians says they won't work on their network if their customer wants to get the xfinity advertised download speeds.  Good luck!

I got a different modem, with DOCSIS 3.1, and my speeds are the same. Clearly the problem is with Xfinity, not my hardware.

@TN_Knox_User 

I am having the EXACT same issue atm. CM700 logs and all are the same. I also have firmware version 1.02.02 and realized from the netgear sight xfinity deployed 1.02.08. Ive spent hours researching and troubleshooting with technicians from xfinity and even reached out to netgear. None of the xfinity techs acknowledged the same exact logs that you pointed out.

I am keeping other isp's in mind throughout this process. I bookmarked this page to see if we can eventually get a resolution. 

My area was also mentioned for infrastructure upgrades and recommending a docsis 3.1. I only have the 400mbps plan, seems unnecessary for an issue that netgear said can be updated "the proper way".

@NoobNetworker don't even bother. Here's my similar situation: https://forums.xfinity.com/conversations/your-home-network/netgear-cm700-getting-only-150mbps-download-speed-with-superfast-service/637a8845384cbc5bcf9d22cd

I got a DOCSIS 3.1 just because I could not stand Xfinity's posture and lack of customer care. Guess what happened with the brand new DOCSIS 3.1 modem? Same speed issues. At this point, we have decided to terminate contract and move on with another provider in the area.

I'm in the same boat.  I am very thankful for all the stress TN_Knox_User has suffered through to get to the root of the problem.  I find it disturbing at the very least how uninformed and apparently untrained many of the Xfinity tech support staff are.  This should be an easy fix IF Xfinity sells the idea you can use your own modem.  It makes one wonder if this is somewhat intentional in order to rent modems from them.  You can't buy one from Xfinity, or at least I haven't been able to do so.  If you do happen to buy one from Ebay or some other place used, they won't let you use it.  I like their internet, but not how they seem to herd us into using only their equipment.  I concur with TN_Knox_User, that their support people try to put the problem back on us too quickly.  I hope TN_Knox_User will keep us up to date as he continues his journey trying to hold Xfinity's feet to the fire...

P.S. FL_LBrewer, you're correct, buying a DOCSIS 3.1 cable modem makes no difference.  I had a friend do just that to no avail.

Follow up to the issue with the slow download speeds with my CM700.

I was told by Comcast support that the only way to resolve the issue was to have a technician come to my house to check the problem.  I scheduled the appointment and he arrived on 2022/11/19.  The technician measured my download speeds with his test device at greater than 1.8Mbps.  So, my cable connection is good.  He said that his experience is that if I want to get download speeds of greater than 400Mbps I'll need to buy a DOCSIS 3.1 modem even though xfinity recommends many DOCSIS 3.0 modems on their Device Info website for their 800bps service (i.e. the CM700).  So, I'm still at the 400Mbps speed with my CM700.  I may just live with it for now.  I don't want to go spend $200 for a new modem, after I just bought a new one based upon xfinity's recommendation.  The technician also said that xfinity in our area only rents DOCSIS 3.1 modems made by Motorola and Arris.  So, those are the only ones that will work on my local network.  I wish I had known this information ahead of time.  It would have prevented a lot of frustration.

... About a week later I received a bill for the technician service call for over $115.  I called customer support about the fee and they said there was a notation on the invoice for "Customer Education".  I questioned the charges and they ended up crediting the charges to my account.

... I decided to "downgrade" to my CM500 modem.  I now get 500Mbps download speed instead of the 400Mbps speed with the CM700.

It's hard to imagine that the Comcast systems engineers are so disconnected from their support people and their field technicians.  No one except the field technicians know what their customers are experiencing.  It seems that Comcast would have far less support calls, spend much less money, and have fewer dissatisfied customers if they could provide feedback to one another for the benefit of all.  Someone should fire the person or people in Comcast leadership for their lack of controls within this organization.  Comcast tells us that they're customer focused and want to meet our needs, but the real world experiences and evidence proves otherwise.

I'm going to continue with my CM500 because I've spent too much time trying to get Comcast to provide the service that I'm paying for, but they fail to deliver!  Seems like fraudulent business practices to me. [Edited: inflammatory remarks and solicitation]