Mesh satellite backhaul caps wired speeds far below fiber plan

The most likely cause is that the Deco 25 is a 2-unit mesh with a dual-band wireless backhaul, and when a wired device sits on a satellite node, traffic between the main unit and that node still has to cross the wireless link (or a slower Ethernet port), so you don't get the full 2 Gbps. 1. Connect your PC directly to the main Deco unit (the one plugged into the modem) with an Ethernet cable and run a speed test. This shows whether the problem is the mesh itself or the satellite path. 2. Check the Ethernet port speed on your PC. Open Windows Settings > Network & Internet > Ethernet (or Wi-Fi properties) and confirm the link speed reads 2.5 Gbps or 1 Gbps. A 1 Gbps link caps you near 940 Mbps regardless of the router. 3. Make sure the Deco's wired backhaul is used if your model supports it. In the Deco app, open the satellite's settings and look for a wired backhaul or Ethernet backhaul option, then re-test. 4. Move the satellite closer to the main unit, or check for a dedicated backhaul band in the app. Wireless backhaul typically loses a large share of throughput over distance and walls. 5. Confirm your modem and the cable from modem to Deco are rated for 2 Gbps. Use Cat6 or better. 6. Test on a macOS or Windows machine with a wired connection to the main unit, and avoid Wi-Fi during the test, since Wi-Fi clients always run slower than wired ones. 7. Restart the modem, the main Deco, and the satellite in that order, then retest. If none of this works: contact Deco (TP-Link) support with your speed test results from steps 1 and 3, and ask your ISP to confirm the line is delivering 2 Gbps at the modem.