Diagnosis
QoS (Quality of Service) or traffic monitoring features are enabled and throttling your connection. They cap maximum throughput.
How to Fix It
Disable all QoS and traffic analysis services.
- Log in, go to Adaptive QoS > QoS tab.
- Set QoS to Disabled.
- Go to Adaptive QoS > Bandwidth Monitor and set Bandwidth Monitor to Disabled.
- Go to Traffic Analyzer > Statistic and set Traffic Analyzer to Disabled.
- Run a speed test again. Speed should now match your modem.
If That Didn't Work
Check for a faulty Ethernet cable or port. Try a different CAT5e or CAT6 cable between your modem and the router's WAN port, and between the router and your test computer. Also, test with a different LAN port (yellow) on the router.
Heads Up
Enabling any hardware-accelerated feature like VPN (Instant Guard, OpenVPN) will drastically reduce maximum WAN-to-LAN throughput. For full gigabit speeds, these must remain off.