Question: My MacBook Pro is dragging my network speed down on all of my Apple devices
I have a MacBook Pro from late 2016. Has a 2.2 GHz Intel Core I7, 16 G memory 1600 MHz DDR3, Intel Iris Pro 1536 MB. WiFi router is a AirPort Extreme running on Version 7.7.7. I am not running virus software at this time but prior to these problems was running Avast. I have Windows Version 16.10
I see 8 wireless clients listed, the MacBook Pro, HP printer, iPad, wife's iPhone, but I don't see my IPhone IP address and I see 4 IP addresses that I don't know what the devices are, maybe Direct TV box and/or Samsung smart TV and/or Blue Ray player. My ISP is a rural phone co-op. My DSL internet speed is about 10 mbps download and 1 mbps upload.
The problem: When I connect the MacBook Pro to the WiFi network it drags the WiFi speed down on all of the devices. The two iPhones and one iPad all will not operate on the WiFi at normal operating speed. When I take the MacBook Pro off of the WiFi all of the other devices return to running normal speed over the WiFi. I carried my MacBook to a neighbor's house and connected to his WiFi and he experienced the same problem. All "I" devices worked fine over his WiFi when I was not connected, but when I connect my MacBook to his WiFi, all of his devices experienced slow performance over his WiFi network.
My ISP tech directly connected his MacBook to the modem via ethernet cable and did not have a speed problem. Ping rate was below 20 mls and speed test was about 9.6 mbps. Did the same with my MacBook and speed problem occurred via ethernet cable. Ping test was 700 mls and speed test timed out.
Contacted Apple Support via phone twice. Neither person had ever seen on device drag down WiFi for other devices. They tried to help but were not able to resolve the problem. Closest Apple Store is 2 hours away. Carried MacBook to local Apple certified service center. They too had never scene a device drag down WiFi They ran diagnostics and found nothing. They wiped my machine and reinstalled OS. I reinstalled Windors 16.10 and everything worked fine for about a month, then same issue again. Took back to service center a few days ago, they ran diagnostics and found nothing, looked for Malware and found nothing, did a speed test, side-by-side with another MBP and saw no significant difference between the two. Their internet speed is roughly 60 times faster then mine. Again, they wiped the machine clean and reinstalled High Sierra. I reloaded MS Office and worked for about four days. Today, I started having the same issue.
MacBook Pro with Retina display, macOS High Sierra (10.13.3)