These tests are all run using CRS326-24G-2S+ switches.
Running the RJ10 is not possible at 10Gbit/s on the CRS326-24G-2S+. It will hit 95°C in less than 10 minutes even without load @ 22°C ambient.
Adding small heat sinks can help a few degrees, making the unit level out at 94-95°C @ 22°C ambient, the minute ambient rises unit thermal limits again.
We have found there is a 20°C difference between running the RJ10 at 10Gbit/s and at 5Gbit/s. But since ROS does not honor any changes to the advertised speeds there is only one way to get the unit to negotiate 5Gbit/s. Make the cable of sufficiently poor quality until only 5Gbit/s is possible and the device will fall inline.
We do a lot of newer office buildings that all have CAT6 or 6A, that will link at 10Gbit/s, but we found that replacing the high grade patch cable on one end with 1-2 meters of CAT5e will make the RJ10 negotiate 5Gbit/s every time and temperature on a passively cooled unit drops to a steady 75°C.
Length of the CAT5 will obvs depend on the quality and length of the full run, but maybe someone can test a CAT3 insert on a very short run? (e.g. this coupler rated at cat 3)
