Slow download speed with Aris Surfboard SB8200 & TP-Link Deco X55

  • 17 March 2023
  • 1 reply


A little background first - my COX account is for 500 Mbps, and with the
Gateway speed tests on the COX website were somewhat greater than 500 Mbps.  
However, we experienced daily issues with the WiFi, having to reboot the
Gateway at least once almost every day.  Our laptops and other devices
would lose connection fairly frequently.

So, I recently replaced my COX Panoramic Gateway with an Arris SB8200
cable modem connecting to a TP-Link Deco X55 (AX3000) mesh system (3 nodes).  
The setup was easy and our devices don't seem to have any issues connecting.
However, download speed tests are now showing 80 Mbps (upload ~10 Mbps).  
A wired test with my laptop connected directly to a Deco node showed only
a slightly higher download speed of 85 Mbps.

According to COX my modem was provisioned properly and it all looks good on their end.

So I sent a detailed report to TP-Link support, including all
information they requested (various speed tests, network topology, firmware version, etc.).  They responded the same day with:  "Unfortunately, we can assume that your modem might be the one
causing unstable and speed issue to your Deco and other devices.”  They also indicated that because a speed test conducted with the laptop directly connected to the modem via cable showed less
than 100 Mbps, then my laptop could only accommodate up to 100 Mbps speed.  This of course completely ignored the fact that previous speed tests using the same laptop were 500 Mbps or greater.

As for the SB8200 modem, the lights have always shown the following:

Power:     Green
Receive:   Blue
Send:      Green
Online:    Green

The TP-Link Deco "home” unit is placed right next to the modem.  A second unit is two rooms away (~25 feet), and a third is downstairs at the opposite end of the house from the modem (~55 feet).

I read in a similar post in this forum that any splitters should be removed from the coax cable.  A splitter was added to the line coming into the house for a small TV (currently not connected).  Please note that the measured download speeds prior to the splitter being put on the line were the same as I'm seeing now.   

From the Web Manager, the values for the Downstream and Upstream bonded
channels fall within the acceptable ranges.

Any assistance would be greatly appreciated.



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1 reply

Userlevel 3
Badge +27

Hello mdcleary76

                               Basically, slow speed, intermittent connection or no internet access occurs usually out of cable signal level, out of acceptable range and it will be resolved after the power level are adjusted by the service provider. So for this we need to check the cable signal level to confirm what causing this issue to proceed further. Since the lights on the modem shows its working on 3.0 Docsis the speed will be slow, 

Green: Upstream channel is connected in DOCSIS 3.0 mode.
Blue: High-speed Internet connection with upstream channels in DOCSIS 3.1 mode.

Blue - Indicates DOCSIS 3.1 operation (high-speed Internet access) which may not be available in all location.  Check with your service provider for availability in your area. 

Please follow the steps mentioned on the link below to check the cable signal level