FLINT 3 Blocking Windows and Linux Devices from communicating

[mcliff]

I use a custom setup where I use RDP to connect to Framework laptops, one running windows 11 and the other Arch Linux to each other.

If I use my Beryl AX, then the RDP and pinging connections work fine. But the Flint 3 seems to block the Linux Machine from access the windows machine.

When I try to ping the windows machine from the linux machine, though both clients show in the Router, the routing fails entirely. This also causes RDP connections to fail entirely as well.

[will.qiu]

Hi,

Could you help to check the following?

1. Are the Linux and Windows devices connected to the Main Wi-Fi or LAN, rather than the Guest Wi-Fi? (Guest networks have built-in isolation that prevents devices from seeing each other).

2. When switching to the Flint 3, did you select the correct Network Profile (set it to "Private" rather than "Public") on your Windows device? You might also try temporarily disabling the firewall to see if it is blocking local discovery.

3. If you are connected to the Main Wi-Fi, please ensure that AP Isolation is not enabled under Admin Panel -> Network.

4. If you are using MLO Wi-Fi, please try connecting to a specific, separate frequency band (e.g., 6GHz, 5GHz or 2.4GHz only) to see if local connectivity returns to normal.

[mcliff]

Yes it does seem to be linked to MLO!

It is odd, linux devices can talk to each other, but windows and linux machines cannot communicate properly when they are on different bands of the WIFI connection.

[will.qiu]

Do you mean that:

• Both the Linux and Windows devices are connected to the MLO SSID.
• However, they might be using different combinations of bands (e.g., Linux is on 2.4GHz + 5GHz, while Windows is on 5GHz + 6GHz).
• In this scenario, the Linux and Windows devices are unable to communicate with each other?

If our understanding is correct, could you please perform the following checks:

1. ARP Table Check: Are both Linux and Windows correctly processing ARP (Address Resolution Protocol)? Please run these commands and check if the other device's IP and MAC address appear in the list:

   # On Windows CMD
   arp -a
   
   # On Linux 
   ip neighbour
   

2. Frequency Isolation Test: If you connect both Windows and Linux to a standalone 5GHz band (instead of the MLO SSID), does the problem still occur?

[badboi]

I just encountered the same issue:

Clients on Wifi cannot see eachother (cannot ping eachother), even tough AP isolation was disabled.

Strange enough, clients from LAN could reach Wifi clients.

All of that happend, after I setup a VPN. Even when the VPN was turned off.

That behaviour is a bug in the software after V 4.xxx, obviously there is no fix for it. but I found a workaround:

First: Find out, if that is your issue: On the impacted client do a ping and look, if there is a arp entry (arp -a), if not: the bug hit you.

I added this script into the LUCI local startup (System→Startup→Local Startup) directly in lines before the “exit 0”

# --- Workaround Flint3 WLAN-ARP-Bug ---
sleep 15

for i in /proc/sys/net/ipv4/conf/*; do
    [ -d "$i" ] || continue
    IFACE="$(basename "$i")"
    
    case "$IFACE" in
        phy*-ap* | wlan*)
            echo 1 > "$i/proxy_arp" 2>/dev/null
            ;;
    esac
done
# --- End Workaround ---

It will configure proxy arp at every reboot. After reboot you will see the proper arp entry, and the connectivity is restored.

Regards

Michael

[will.qiu]

Hi

Thank you for sharing your experience. It is possible that certain devices are having issues with Wi-Fi broadcast/multicast support.

You can consider SSHing into the router and running the following commands to see if they fix the issue. Modifying the kernel parameters directly like what you have done is also a valid approach.

# Enable the Proxy ARP 
uci set wireless.wifi2g.proxy_arp='1'
uci set wireless.wifi5g.proxy_arp='1'
uci set wireless.wifi6g.proxy_arp='1'
uci set wireless.wlanmld2g.proxy_arp='1'
uci set wireless.wlanmld5g.proxy_arp='1'
uci set wireless.wlanmld6g.proxy_arp='1'

# Enable the Multicast to Unicast
uci set wireless.wifi2g.multicast_to_unicast_all='1'
uci set wireless.wifi5g.multicast_to_unicast_all='1'
uci set wireless.wifi6g.multicast_to_unicast_all='1'
uci set wireless.wlanmld2g.multicast_to_unicast_all='1'
uci set wireless.wlanmld5g.multicast_to_unicast_all='1'
uci set wireless.wlanmld6g.multicast_to_unicast_all='1'

uci commit 

reboot