1. Background
My ISP technician came to upgrade my broadband plan. When my computer was connected directly to the modem, speeds were normal — hitting over 900 Mbps. However, once I connected my WAVLINK BE3600 router, download speeds dropped to around 500 Mbps.
My setup:
1）New broadband plan
2）Modem in bridge mode, router handling PPPoE dial-up
3）Modem port: 10Gbps | Router port: 1Gbps.
| Modem | Router | Host | Speed Result |
|---|---|---|---|
| PPPoE | Router | Connect to the router | Half Speed |
| PPPoE | - | Directly connect to the optical modem | Full Speed |
| Bridge | PPPoE | Connect to the router | Half Speed |
| Bridge | - | Directly connect to the optical modem and dial | Half Speed |
Summary: The broadband speed will be full only when the modem dials up and the host's network cable is directly plugged into the modem.
Everyone's situation may vary, but you can follow the test plan in the table above to determine which link is causing the problem.
If this article's solution does not solve your problem, you can also follow the test plan in the table to perform tests and analyze the problem based on the results.
2. The Fix
The problem was caused by the modem’s settings — not the router.
Solution:
1）Disable the IPv4 firewall on the modem
(recommend turning off IPv6 firewall as well for future-proofing)
2）Turn off QoS on the modem
3. Extra Steps (If Needed)
After the changes above, my speed was back to normal. If yours isn’t, try these (optional steps):
1）Disable QoS on your router
2）Set the router to AP mode
4. My Debugging Journey
~The ISP technician visited, replaced the modem, checked the backend — no improvement.
~I also tried solutions I found online, like changing the router's MAC address in bridge mode and even replacing the router itself, but none of these made a difference.
I tried spoofing the router’s MAC address, switching routers — still no luck.
According to the technician, their system has a MAC allowlist; changing it yourself may not help and could even reduce speeds.
Based on other users’ reports, whether MAC spoofing works depends on your ISP and region — check with your provider.
Hope this helps anyone facing similar issues! Feel free to share your experience or ask questions below.
