Flint 3 (GL-BE9300) LAN Port Flapping with Philips Hue Bridge v2

Routers
1

Hardware: GL-BE9300 (Flint 3) Firmware: 4.8.4 Device in conflict: Philips Hue Bridge v2 (100Mbps Ethernet)

The Issue: My Hue Bridge cannot maintain a stable physical link with the Flint 3. The device is experiencing "Port Flapping"… the connection resets every few seconds, preventing the Bridge from reaching the internet (3rd light remains off).

Evidence from Kernel Logs: The logs show the internal switch brain (rtl8372-mdio) cycling the link status continuously:

  • kern.info kernel: rtl8372-mdio 90000.mdio:1d: lan2 link up, speed 100

  • kern.info kernel: rtl8372-mdio 90000.mdio:1d: lan2 link down (This cycle repeats indefinitely on LAN ports 2 and 4.)

Troubleshooting already completed:

  1. Cables: Tested with high-quality Cat6 and a legacy 4-wire Cat5 (designed to force 100Mbps). No change; the port still flaps.

  2. Software: Disabled "Network Acceleration" (Hardware/Software Flow Offloading). No change.

  3. Manual Speed Forcing: Attempted to use ethtool via SSH to lock the port to 100 duplex full autoneg off. This failed with "No such device" or "Not supported" because the ports are part of the eth1 virtual switch bucket and do not appear as individual hardware interfaces to the kernel.

  4. Cross-Verification: The Hue Bridge works instantly and perfectly when plugged into a 1Gbps port on an older router (FritzBox), proving the Bridge and cables are functional.

Specific Questions for Support:

  1. Is there a known incompatibility between the rtl8372 Switch IC in the Flint 3 and legacy 10/100 Ethernet controllers?

  2. How can I manually force a single physical LAN port to 100Mbps without affecting the entire eth1 switch? Standard ethtool commands against eth1 or br-lan are not effective.

  3. Is there a way to adjust the Auto-Negotiation timing or sensitivity to allow these older IoT controllers to sync?

Thank you for any support! <3

2

I have similar experiences with 100 Mbps devices on my Flint 3 (Firmware 4.8.99 Beta).

My TV on lan3 (100 Mbps) shows the same port flapping behavior:

lan3 link up, speed 100
lan3 link down
lan3 link up, speed 100

Interestingly, my Xbox on lan2 (1 Gbps) also shows occasional link flaps:

lan2 link up, speed 1000
lan2 link down      ← after 5-6 seconds
lan2 link up, speed 1000

But despite the flapping in the logs, the Xbox runs stable with no noticeable connection issues. So the link flaps don't always mean actual connectivity problems.

GL.iNet support suggested an EEE (Energy Efficient Ethernet) fix:

echo "w 7 60 0" > /sys/kernel/debug/rtl8221/phy_reg

However, this broke 100 Mbps connectivity completely - devices got link up but no DHCP/traffic.

Workarounds to try:

  • Test different LAN ports (the RTL8372 switch ports may behave slightly differently)
  • Put a simple unmanaged gigabit switch between the Hue Bridge and Flint 3

It seems to be a known RTL8372 switch compatibility issue with certain 100 Mbps devices. The switch may have problems with auto-negotiation or EEE handshake on slower links.

1 Like
3

any recommendation or where to search? I don’t want to spend too much money to make it work :sweat_smile:

Tested with all ports, none of them work.

4

Only for testing maybe this is ok:

5

thanks for the pick!

But that’s too much to get working an old HUE Bridge which costs around 70$

I thought it would be cheaper :frowning: