First off, check if your modem can really handle with that. If you are using wi-fi probably you will not achieve. (tip: use a direct cable)
After that, check your driver settings:
- Set Jumbo Frame (or Jumbo Packet) to the maximum supported value, for example, 9014 bytes. Gigabit Ethernet controllers that support jumbo frames can transfer packet sizes larger than the standard Ethernet frame size (1500 bytes).
- Set Receive Buffers (or Receive Descriptors) to the maximum supported value, for example, 2048. For some Ethernet controller drivers, this setting is grouped under Performance Options.
- Confirm that Link Speed & Duplex is set to Auto Negotiation (or Auto Detect