I bought Deco M4 recently (FW 1.5.6 Build 20221229 Rel. 72252) to extend the network coverage, but cant get more than 100 mbit from it.

Configuration

Main TP link modem -> TP-link 1Gb switch -> Deco (main) - > Deco 2 -> Deco 3

Troubleshooting

1. tested wired network w/o Deco -> 1Gb speed

2. attached main Deco -> drop to 100 Mbit even for wired devices (tested ib both modes router ( QoS set to 1000) / AP)

3. attached all 3 Decos -> drop to 100 Mbit even for wired devices (tested ib both modes router ( QoS set to 1000) / AP)

4. Returned back to original config as I thought something is wrong with the cable: Main TP link modem -> TP-link 1Gb switch -> Archer C6 -> but speed is back to 980 Mbit

Any thoughts what could be wrong here?

Thanks