GL-BE9300 (Flint 3) LAN port issue - wired clients lose Internet connectivity depending on LAN port (Firmware 4.9.0)

Router
1

Device

GL.iNet Flint 3 (GL-BE9300)

Firmware

4.9.0 (stable)

Network Topology

Orange FunBox
        |
      WAN
        |
   Flint 3
     |      |
   LAN1   LAN2
    |       |
 Switch 1  Switch 2
    |       |
 PC + TV   TV
 Orange    Orange
 IPTV      IPTV
 decoder   decoder

Issue

I can consistently reproduce a problem related to the LAN ports on my Flint 3.

The same unmanaged Ethernet switch with the same connected devices behaves differently depending on which LAN port of the Flint 3 is used.

When the switch is connected to one LAN port, all connected devices work normally.

When the same switch is moved to another LAN port, some wired devices lose Internet connectivity.

The problem can also be reproduced when two unmanaged Ethernet switches are connected simultaneously to two different LAN ports of the Flint 3. Devices connected through one of the switches may lose Internet connectivity.

Observations

  • The WAN connection is stable and working correctly.

  • DHCP, NAT, DNS and routing are functioning normally.

  • The router itself has full Internet connectivity.

  • Devices connected directly to the Orange FunBox work correctly.

  • The same unmanaged Ethernet switch behaves differently depending on which Flint 3 LAN port is used.

  • The same Ethernet cables and the same client devices were used during testing.

  • The Orange IPTV decoder and Smart TV work correctly when connected through one LAN port.

  • The Orange IPTV decoder and Smart TV lose Internet connectivity when the same switch is connected to another LAN port.

  • During one test, after moving the switch to LAN1, the Orange IPTV decoder immediately regained Internet access.

  • The issue appears to follow the physical LAN port rather than the Ethernet cable, switch or connected devices.

Troubleshooting Performed

  • Factory reset.

  • Configured the router from scratch.

  • Tested multiple Ethernet cables.

  • Tested multiple unmanaged Ethernet switches.

  • Moved the same switch between different LAN ports.

  • Tested with two switches connected simultaneously to different LAN ports.

  • Verified DHCP leases.

  • Verified routing.

  • Verified multicast configuration.

  • Captured IGMP traffic using tcpdump.

  • Checked multicast routing tables.

  • Confirmed that the router itself has full Internet connectivity.

Expected Behavior

All LAN ports should provide identical functionality.

The same unmanaged Ethernet switch and the same connected devices should work normally regardless of which LAN port is used.

Two unmanaged Ethernet switches connected simultaneously to different LAN ports should also work correctly, with all connected devices having Internet access.

Actual Behavior

Internet connectivity for wired devices depends on which physical LAN port of the Flint 3 is used.

Moving the same switch with the same devices between LAN ports changes whether the Orange IPTV decoder and Smart TV have Internet access.

Could you please investigate whether this could be a firmware issue affecting the integrated LAN switch, VLAN configuration, bridge configuration, or Ethernet driver in firmware version 4.9.0?

Additional information

Both Ethernet switches used during testing are unmanaged switches.

They have no VLAN configuration, no STP configuration, no LACP, and no advanced network features.

The issue occurs with simple plug-and-play unmanaged switches.

3

Hi,

Thank you for the detailed information and the troubleshooting you have already performed.

We performed a local test, but have not been able to reproduce the same issue so far.
To help us narrow down the conditions under which it occurs, could you please help confirm the following points?

  1. When one of the affected devices is connected directly to each Flint 3 LAN port without the switch, does it have Internet access on every port?
  2. When the issue occurs, do all devices behind that switch lose Internet access, or only some of them? Please also let us know which devices are affected.
  3. If the issue can be reproduced again, please SSH into the Flint 3 and start the packet capture before moving the switch:
tcpdump -ni any -e -s0 -w /tmp/lan-port-test.pcap &
echo $! > /tmp/tcpdump.pid

Before moving the switch, please run the following commands and take a screenshot of the output:

date
bridge link show
bridge fdb show br br-lan
ip neigh show dev br-lan
bridge mdb show

Then move the switch from the working LAN port to the LAN port where the issue occurs. Once the affected devices lose connectivity, run the same commands again and take another screenshot.
Then stop the packet capture:

kill "$(cat /tmp/tcpdump.pid)"

Could you please export the system log from the Flint 3 after the issue occurs, and send the following information to us via private message:

/tmp/lan-port-test.pcap
The exported system log
The screenshots taken before and after moving the switch

image
image497×179 13 KB

Thank you for your understanding and cooperation.