I got 1 Gbps fibre connection FTTH coming to Fritz 4040. As that router got no guest network nor bandwith management I decided to connect it by cable to TP-Link VR900 in wireless router mode throgh cat 5 cable into LAN/WAN port in TP-Link. Unfortunatelu TP-Link provides up to 100 mbps connections. I started to troubleshoot and logged in to webGUI of Fritz. Fritz showed ethernet connection between Fritz and TP-Link as 100 mbps only ! Why ? I thought and all specs shows that TP-Link is gigabit router with gigabit ethernet ports ... What is wrong in my configuration ?

Thanks.