Hi.  I have an old mac pro and have connected a powerline TL-PA7010 to run ethernet to it.

According to the TPLink Utility, I'm getting 300-340 mbps between the powerline units, which is pretty much exactly as expected.

HOWEVER, the internet speed test results on the mac itself are closer to 100mbps or less.  Somehow over the final five feet I'm losing 2/3rds the datarate.

So I'm wondering if I have some setting issues that are causing poor communication between the powerline and my mac.  Or does this mean I have a conflict going on elsewhere with my router or modem?  I'm not sure where the bottleneck might be.  If the powerlines are measuring traffic accurately, then it seems it has to be my network setting on my mac?. The ethernet cards on my mac are old but they are Intel 82574L cards which are gigabit cards.  The powerlines are connected to an Apple Airport Extreme wifi router that is connected to a Spectrum modem.  There is iPv6 conflict apparently with Spectrum so I have iPv6 set to local-link on the Airport and I did the same for the ethernet connection on the mac desktop.

I'm kinda clueless on proper network settings so not sure what might need to be changed or tested beyond hit and miss.  To make matters worse, the Spectrum tech that installed the modem could not give me any information at all about proper DNS or other settings, so not sure anything is correct.

The rest of the house is running on the wifi network and getting around 300 mbps downloads on 5g.  Its just this hardwired mac that I can't figure out if I have something set wrong.  

Any advice?  Point me somewhere?  thanks!