Hi, I'm having the same issue -- getting 200 mbps down/42 mbps up at best. Since this issue started I've been running speed tests frequently and I'd say I'm averaging 100 mbps down/35 mbps up. I've had 3 visits from service techs, the most recent was a tech and his supervisor. After confirming that my signals measured at the modem are within spec and that the modem boot filename contained 'sb8200-gigabit' we tried:
1. Replaced coax cable coming into the house up to the modem. I have no splitters installed and the outdoor wiring and connections were replaced when I moved in last year. We did this because we found a cracked portion while visually inspecting it. Improved noise levels slightly, but no change in speed test results.
2. Checking speeds on 4 different sites (speedof.me, fast.com, speedtest.net, speedtest.xfinity.com) through my modem (SB8200) and router (Netgear R7000) over wifi and ethernet. We then went direct from the modem with a known good CAT6 cable. I've used multiple devices (a surface book laptop, an HP elitebook 850 g2 laptop, comcast tech laptop, etc.)
3. Bypassed my modem and used a comcast speed testing modem.
4. Tried going back to my SB 6183 just to see if it made a difference, I used it in a different state with 350 mbps down service so I know this modem-router combination can exceed 250 mbps. Still 200/43 max.
Sounds like they now believe it is a problem or misconfiguration at the CMTS. Doing a bit of googling it looks like there IS an upgrade that needs to happen in order for the CMTS to support DOCSIS 3.1. This certainly makes sense to me--seeing repeated test results where I get something like 199.9 mbps or 200.1 it sure does seem like my speed is still being capped at some point in the network.
A friend of mine, who lives about 5 miles away, upgraded to the gigabit service the same day I did and was getting ~950 mbps within an hour of calling in to change his service.
The local service techs have been great, and I understand that this is a new service being provided by Comcast but man oh man I have experienced the WORST support over the phone. Having to repeat my entire issue and service history to each person I speak to, rude people in billing just disconnecting me when I ask whether I am going to be billed for the gigabit service even though I'm regularly getting 10% of that on speed tests. Almost every single tech person on the phone has told me different conflicting information.
I had to take off half a day from work and then spend 2 weekend days working with the techs, and have probably spent more than 5 hours on the phone. Absurd.
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