Earlier this year, I was having trouble with mobile devices connecting to my home WiFi and often my desktop computer (connected via Ethernet) would seem to not connect to the internet. My ISP (Last Mile Wireless Internet) checked my connection and it found no issues. None of the other customers using this tower were reporting any issues either. They told me that the only way to test the router is to bypass the router and connect directly into the modem to see if there is any difference. My ISP does not like D-Link and recommended ANY router made by Asus or TP-Link.
Since I was using an old D-Link EBR-2310 router (in the detached garage beside the tower), it was a bit inconvenient for me to try bypassing the router because my good laptop fried. I found that Amazon had a cheap wireless router for $20 (TP-Link TL-WR841N) that appeared to have really good reviews so I thought I would try it instead. The TL-WR841N was a big improvement in WiFi connectivity but my download speeds since the spring of 2018 have been verrry slow. For example, I was trying to download a large file and the download speed is around 20-40 KB/s and the process had already failed several times. I used to get 5-10 Mbps (625-1250 KB/s, using Ookla Speedtest) when the EBR-2310 was working better. Sometimes, rebooting the TL-WR841N improved its performance somewhat but not spectacularly.
To check the various devices, I found a long Ethernet patch cord and fired up my old Thinkpad T30 laptop. I discovered that, when I downloaded that same large file, my download speed (reported by Firefox) increased to 200-400 KB/s at both the router and at the tower switch. I then went to the Ethernet distribution panel in my house and found that connecting directly into the cable coming from my router also gave me a 200-400 KB/s download speed.
When I plugged my laptop into one of the ports in the EZXS88W switch, my file download speed dropped back down to the 20-30 KB/s range. Moving the router cable to a different port in the EZXS88W seems to have gotten my other devices to now have faster internet connection speeds.
Last Mile Wireless has responsive tech support and, after letting them know that my internet speed still seemed to be a bit on the slow side, they rebooted their antennas. That got my connection speed back into the 5-10 Mbps range again.