Often the cause of wired speeds on a fibre connection being slower through the router than the ONT is because of a setting called QoS (or Quality of Service). QoS is a setting that is designed to set priorities or caps on your devices' speeds from the router itself.
If you're using a D-Link DIR 882 from us you want to login to your router (this is done by entering the IP address 192.168.0.1 in the address bar - and then entering your username/password). Find the QoS Engine settings and ensure both upload and download limits are set to the maximum of 999Mb/s. If you have devices in the priority queues you may also want to remove them.
Other third party routers may have a similar setting to this one you may want to change - sometimes called similar names like "bandwidth control" or "traffic manager".
If you are unable to find a setting like this it may be worth while locating the Factory Reset button on your router and pressing this in with a thing long object - like a pin or paperclip - for 10 seconds until the device reboots. A factory reset will help remove any non-default configuration. Once the router reboots you normally want to run its check for firmware updates to ensure that it has the latest software.
Please note that if you reset your router, it will reset any settings you have manually configured, such as Wireless Passwords or Port Forwarding.
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