I've had Gbit service plan for quite a while. A few years or more. I've had multiple modems as well. Arris, Technicolor, etc. The main issue is of course, I never really get close to Gbit speeds. Every speed test I've done caps out around 600Mbps. I can't even list all the things I've tried because I don't have all day to post it. But here are a few things I've tried.
Tech visit. I bought my house new. All new RG6 wiring. Direct runs to each room. Cable modem has it's own special line. Levels are fantastic. No noise issues, levels are great. No negative events in the logs either.
Replaced modem. Just for the heck of it.
Used it in bridged mode and non-bridged mode. With or without my own router.
Factory defaults reset. Multiple times.
Tried different speed test sites.
Something was changed or done at a particular time because I do download a lot from the usenet groups which all have unlimited speeds. I connect to multiple usenet services at once and did have around 105MB/sec which was great! I would see my download speeds consistent at that speed for the whole time it was downloading. Then at some point that number dropped to 73MB/sec which is around 600Mbit. I don't know if it was the bootfile or what, but it does seem my speeds are capped now at that speed. Not sure where to go, or what to do but if I'm only getting %60 of my constant speed shouldn't I get %40 refund every month? Considering to lowering my service plan since Xfinity doesn't seem to handle Gbit speeds to well. Any suggestions on this?