Reduced Wi-Fi data rates when network switch added between two Deco M5s
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I ran an experiment whose results I am trying to understand.
I have a deco M5 in my basement connected to my Verizon FIOS box via Ethernet. This is my main router. I then ran Ethernet from there to my Deco M5 in my living room. When I use the Speedtest app both in the basement and the living room (on Wi-Fi) I obtain about 300 Mbps (essentially the max from my service provider). This is great but not the configuration I need.
Then I changed things up by inserting a 5-port TP-Link 5 port gigabit unmanaged network switch in the middle. Specifically it's this one: TL-SG1005D. To be clear the setup is fios box to basement router. Basement router to 5 port switch, and 5 port switch to upstairs Deco. I did this so I could connect other items to the switch (one of these is actually a 24-port gigabit network switch also made by tp link). When I run speedtest via Wi-Fi in the basement I get about 300 Mbps again. When I run speedtest on an ethernet connected laptop to the 24-port switch I also get 300 Mbps. But when I run speedtest upstairs on Wi-Fi to my upstairs Deco I get maybe 85-90 Mbps.
I'm struggling to understand how the network switch(es) add that much latency. I looked online about if and how switches could do this and all the responses are that switches don't do this and it's something else in the network as a bottleneck. I feel like my simple experiment says otherwise...but it's not totally definitive yet. Any ideas would be appreciated.
85-90 Mbps sounds just right if your Satellite Deco uses WiFi backhaul. Check what it says under Signal Source for Satellite Deco in Deco app: just connecting Satellite Deco to Ethernet cable doesn't guarantee Deco can use Ethernet backhaul.
Expect to see this for Ethernet backhaul:
and this for WiFi backhaul:
Another two possibilities are:
1. Satellite Deco M5 negotiated 100Mbps to the switch, instead of gigabit.
This can be tested by wiring laptop to second port of Satellite M5 and running speed test on laptop.
Also, if you install firmware 1.6 beta on Satellite M5, that firmware will alert when link is less than gigabit. Yet, it is beta, which means it could have its own issues, and also there is no rollback. Forum page with beta firmware: Deco M5 1.6.0
2. Wireless device you use to run speed tests connects to Satellite M5 on 2.4GHz instead of 5GHz.
You can test that by turning off 2.4GHz band on Main Network, in Deco app, and running speed tests again. Verify your mobile device is connected to Satellite M5 before repeating speed tests. If your Satellite Deco can't broadcast on 5GHz (hardware failure), with 2.4GHz turned off your wireless devices will all switch to Main Deco.
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I happened to have that same switch, TL-SG1005D. I run my Deco mesh in AP mode, so my test setup will be different, but if it were switch inherent problems, the difference would not matter.
This is how I connected them together for my speed test:
ISP Router<--Ethernet-->TL-SG1005D<--Ethernet-->Satellite M5
I ran speed test on smartphone connected to that Satellite Deco. I got 370Mbps on first run and 465Mbps on second run. My home Internet is gigabit.
