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Not getting HALF of my purchased speed

Frequent Visitor

Not getting HALF of my purchased speed

I recently upgraded to Comcast's 250Mb/s service.  The modem I had at the time (Cisco DPC3008) is rated to support speeds up to 320Mb/s, so I expected it to work.  My results were around 100Mb/s, and Comcast sent an email saying my equipment needed to be upgraded to support the new, higher speed.

 

From the Comcast compatibility page, I selected the Linksys CM3016.  It's rated to support a maximum speed of 686Mb/s, so I expected it would run at 250Mb/s with no issue.  I saw very little improvement, maybe speeds up to 125Mb/s, still only half of what my plan called for.

 

I spent an agonizing hour or so on the phone with tech support as they 'adjusted' my signal.  When they were done, my speed had dropped back BELOW my previous plan (18Mb/s).   They finally got the speed back up to ~120Mb/s, then told me my modem was defective.

 

I tested my speeds during the night - at 2am my speed was 228Mb/s, but by 5am that had dropped off to less than 150Mb/s, and by 8am, my speeds were back to under 120Mb/s, less than half the quoted speed for the service.  That tells me the issue was never my modem, it was Comcast network congestion.  Instead of admitting that, Comcast pointed the finger at customer-owned equipment and hoped I'd never figure it out.

Gold Problem Solver

Re: Not getting HALF of my purchased speed


@RegularGuy99 wrote: ... I selected the Linksys CM3016.  It's rated to support a maximum speed of 686Mb/s ...

686Mbps is a theoretical value that you'll never see in the real world. Comcast rates the CM3016 at "Up to 373 Mbps" (see https://mydeviceinfo.xfinity.com/device/linksys-cm3016-545).

 

Are you connected via Wifi or Ethernet?

If you want to troubleshoot this yourself, please see Connection Troubleshooting Tips. If you still need help, please provide Information Requested for Connection-Related Posts.

Frequent Visitor

Re: Not getting HALF of my purchased speed

Ok, I see Comcast's comment about 373Mb/s being the top speed.  I have 250Mb/s service, so I should be able to see speeds approaching 250, no?  I'm not.  I'm getting half that much, or less.

 

HARD WIRED ETHERNET - People keep pointing out that you won't get as high a speed on wireless.  I am NOT using wireless.  Again, NOT using wireless.  I am using Ethernet Cat6 cables.  One from the modem to my router is 3ft long, the other from my router to my PC's Gigabit Ethernet adapter is 6ft long.

 

To humor Comcast, I've removed the router during tests and had only ONE device - an Intel i5 PC running Windows 10 Pro - connected DIRECTLY from the modem to my PC's Gigabit Ethernet adapter.  Speeds do not improve when directly connected PC-to-modem.

Silver Problem Solver

Re: Not getting HALF of my purchased speed


@RegularGuy99 wrote:

Ok, I see Comcast's comment about 373Mb/s being the top speed.  I have 250Mb/s service, so I should be able to see speeds approaching 250, no?  I'm not.  I'm getting half that much, or less.

 

HARD WIRED ETHERNET - People keep pointing out that you won't get as high a speed on wireless.  I am NOT using wireless.  Again, NOT using wireless.  I am using Ethernet Cat6 cables.  One from the modem to my router is 3ft long, the other from my router to my PC's Gigabit Ethernet adapter is 6ft long.

 

To humor Comcast, I've removed the router during tests and had only ONE device - an Intel i5 PC running Windows 10 Pro - connected DIRECTLY from the modem to my PC's Gigabit Ethernet adapter.  Speeds do not improve when directly connected PC-to-modem.


https://forums.xfinity.com/t5/Your-Home-Network/Video-10-things-you-can-do-right-now-to-fix-your-int...


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I am just a customer, volunteering my time to help other customers here in the Forums.
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Gold Problem Solver

Re: Not getting HALF of my purchased speed


@RegularGuy99 wrote: ... I have 250Mb/s service, so I should be able to see speeds approaching 250, no? ...

Yes. Your fellow customers here have no access to your account information or signal status, so as stated, if you want to troubleshoot this yourself and still need help, please provide Information Requested for Connection-Related Posts.


If you can't find the problem or you'd rather have Comcast do the troubleshooting, call them at the phone number on your bill or 1-800-Comcast, or chat with them using the Internet Support option at https://support.xfinity.com/chat. If they can't fix the problem remotely, insist they send a tech out to identify the cause and correct it.

If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan (https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast rental device, or anything outside your home, you shouldn't be charged.

Frequent Visitor

Re: Not getting HALF of my purchased speed

Thank you for the reply.

 

Comcast's remote troubleshooting has made the problem worse, not better.

As for any splitters, etc., the configuration inside my home is the same one Comcast installed several years ago.  I haven't added anything, I haven't removed anything.

The only change was my upgrade to the 250Mb/s service, and (at Comcast's insistence) a new modem capable of handing the increased speed.

My big fear is that if Comcast does dispatch, I am going to be billed for that service call.

 

I'm not in an AT&T Fiber service area, but there is a new ISP that is delivering up to Gigabit speeds in my area.  I've ordered service from them.  Once they've installed, I'll compare them to Comcast.  If Comcast is still only delivering half the speed, they will be removed.

Frequent Visitor

Re: Not getting HALF of my purchased speed

To further humor Comcast, I purchased another new modem.  This one is an ARRIS Surfboard SB6183.

It practically took an Act of Congress to get the Comcast tech to understand I wanted a new modem provisioned, but he finally got it.  He got the MAC address wrong FIVE times, and got the wrong modem model TWICE.

Now that it's connected, I tested my line speeds again.  With my router in the configuration, I get 118Mb/s.  With my router removed - a straight Cat6 cable from PC to modem - I get 120Mb/s.   I have 250Mb/s service.

My new ISP should be installed by the end of next week.  Then it will be time for a good, old-fashioned shootout between them and Comcast.

Official Employee

Re: Not getting HALF of my purchased speed

Hello RegularGuy99, I know your time is valuable and I appreciate you taking the time out of your busy day to create a post on our forum. Please allow me the opportunity to make this right for you, I am sure that I can help you with obtaining the full 250 mbps speeds that you subscribe to. To move forward please send me a private message with your full name and account number. 


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Official Employee

Re: Not getting HALF of my purchased speed

Hi RegularGuy99, I don't see a private message or a reply back from you here so I will close this thread as completed. Feel free to create another post if you require further assistance, have a good day.


I am an Official Comcast Employee.
Official Employees are from multiple teams within Comcast: CARE, Product, Leadership. We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!