I have a Linksys WRT1900ACS which is a router/gateway to the internet, dhcp server etc. I disabled Wifi on that device. Then I connected two TP-Link Archer A7 v5 using LAN cables (through a switch) to the Linksys router. Both have 5G wifi enabled with the same SSID, using 802.11r Fast Transition.
Using a iperf3 server on the linksys router I run iperf client on the TP-Link routers I get consistently only 250Mbps.
Iperf on a PC connected with a LAN cable to the Linksys gets almost 1Gbps.
I've seen that the TP-Link A7/C7 are limited in the LAN performance. But the surprising thing is that when I do an iperf3 speed test to the linksys iperf3 server on a device connected with WiFi (laptop, iphone) near one of the TP-Link routers I get sometimes as fast as 400Mbps.
So somehow the TP-Link is capable of communicating with the linksys much faster than the 250Mbps limit of the LAN connector. If I connect the same devices via LAN cable to the TP-Link I get only 250Mbps over that link.
I'm just thinking I'm missing something simple that limits the LAN performance of the TP-link to almost exactly 250Mbps.
You are running iPerf3 on the router itself, which means that the packets must be sourced or sinked by the CPU inside the router. This is okay on a general purpose computer (such as an x86 device), but the CPU inside most consumer all-in-one routers cannot achieve this at line rates. They are designed to route and switch traffic very rapidly using specialized hardware, but it is comparatively slow at local processing of those packets.
If you run iPerf3 on two general purpose computers connected to the switch, you should get full gigabit performance (assuming no other issues).
Thank you for clarifying this. I actually mis-stated this: "If I connect the same devices via LAN cable to the TP-Link I get only 250Mbps over that link." - this is wrong. I just tested it and I get over 900Mbps.
So there is no problem. I was originally using the TP link as my gateway, and that's when I was getting disappointing LAN numbers, now, with the linksys they are fine, and I can also use the LAN ports on the TP-link routers and get full performance.
Thank you again and sorry for the misunderstanding.