So it has come to my attention the way comcast verifies and proves you get your speed you pay for is by having a tech come out and use this device https://genesys-industries.com/catv-broadband-equipments-and-accessories/comcast-xm1-wireless-docsis...
To test the hard wired speed. I never in any company have seen this device being used to test the speed.
Can someone tell me if im being lied to? Who is telling me the truth?
FWIW, that device doesn't measure speeds. Some techs carry a tool called an XMT - Ordroid O/S based XMT.
FWIW, the XMT is the single most accurate method of testing speeds on DOCSIS. Far more accurate than any speed testing site or app to date.
Complain persistently to Customer Service !! Ask for a tier 2 rep and / or a supervisor. Good luck !
What else is on your network when you run your download speed test? You mention that you have a 1Gb interface but not how you're connected into your network. Are you fanning your network? Over subscribing an interface? What modem are you using? What router?
If I understand you correctly, when you directly connect your laptop to the modem you see throughputs of 400 Mb - 600 Mb correct? And you are testing from the same site at all times correct?
Have you checked your interface for packet errors or dropped packets? Have you checked your modem for errors both correctable and uncorrectable?
The variance in throughput is troubling especially if you always use the same remote site. Are you finding the throughput increases the more times you run the test?