# wifi routing dies after 30s Source: https://forum.modalai.com/topic/1449/wifi-routing-dies-after-30s Category: General Questions (https://forum.modalai.com/category/2/general-questions) Posted: 2022-10-14 05:26:16 UTC by Patrick Hinchey Replies: 8 · Views: 1682 ## Patrick Hinchey · 2022-10-14 05:26:16 UTC Hi, I have my brand new VOXL2 with a LTE modem/USB hub, and an Alfa AWUS036ACS wifi dongle plugged into that. The wifi is configured in station mode. Both the cellular modem (though it has no SIM card) and the wifi enumerate and give valid IP addresses with ```ifconfig```, and I am able to SSH into the VOXL2 for about 30s after reboot. Then the wifi network routing seems to die. The IP is still listed in ```ifconfig```, and my router web interface still shows the VOXL2 at that address. However I can no longer ping the VOXL2, and on the VOXL2 connected over adb, I can no longer ping the gateway or anything else. It consistently works right after boot for about 30s. Any help is much appreciated, thanks! An excerpt from ```ifconfig``` after it has stopped working: ``` wlan0: flags=4163 mtu 2312 inet 192.168.2.105 netmask 255.255.255.0 broadcast 192.168.2.255 inet6 fe80::c74c:4fe1:b608:26a1 prefixlen 64 scopeid 0x20 ether 00:c0:ca:b1:6c:9f txqueuelen 1000 (Ethernet) RX packets 811 bytes 191916 (191.9 KB) RX errors 0 dropped 119 overruns 0 frame 0 TX packets 99 bytes 15113 (15.1 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 wwan0: flags=4163 mtu 1500 inet 169.254.174.110 netmask 255.255.0.0 broadcast 169.254.255.255 inet6 fe80::f4e6:24dc:20b7:ffe0 prefixlen 64 scopeid 0x20 ether ce:26:e7:9c:b4:6e txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 ``` ## Reply by Steve Turner · 2022-10-14 13:45:18 UTC I don't work for ModalAI and I haven't run this specific configuration but a few things to try: If you remove the LTE Modem does the problem persist? It sounds to me like your default route maybe is changing once the LTE modem comes up. `route -n` will show you all of your routes with `0.0.0.0` pointing to the interface associated with it. ## Reply by Patrick Hinchey · 2022-10-15 03:07:53 UTC Thanks Steve, Pinging the VOXL2 in one terminal window while continuously executing ```route -n``` in adb in another window, I see that first there is nothing in the routing table and the ping says 'host unreachable'. After a few seconds, ```wlan0``` turns up on ```0.0.0.0``` and ```192.168.2.0``` in the routing table, and at the same time the ping starts returning a pong. After about 5 more seconds, ```wwan0``` shows up and everything is still fine. So it looks like the LTE module is not interfering with the WiFi dongle. Here's where it gets interesting. After another few seconds, ```usb0``` appears on ```192.168.2.0``` and then the ping return 'host unreachable'. What's going on here?! It should be noted that the network connectivity craps out even when the VOXL2 is *not* connected via USB, so the timing might be a coincidence. But it is repeatable. This behaviour is also common across two different VOXL2 boards ## Reply by Patrick Hinchey · 2022-10-15 05:20:55 UTC Aha, got it! So ```usb0``` is interfering with WiFi because my route gateway is ```192.168.2.1``` and the interface ```usb0``` insists on using ```192.168.2.0```. If I create use softap mode on the VOXL2 or create a hotspot with my laptop with a different gateway and connect to that, everything works fine. So now connecting back to my home router and using adb to execute ```ip link set usb0 down```, everything works on the main network! Now the question is: this solution doesn't persist across reboot, so how can I force ```usb0``` down on boot? Creating```/etc/network/interfaces``` and setting ```usb``` to a different address doesn't seem to have any effect. I tried to run ```ip link set usb0 down``` in ```~/.bashrc``` but this happens before ```usb0``` goes up and it complains that no such interface exists. I saw something about ```voxl-modem```, but I could only find info on microhard and feather modems. I couldn't find any documentation on using ```voxl-modem``` to disable ```usb0``` @tom how can? ## Reply by Patrick Hinchey · 2022-10-16 18:27:02 UTC Hopefully someone will reply on Monday with a cleaner approach, but I had some time on Saturday, so I've seconded voxl-static-ip in a hacky way. This has enabled me to keep working through the weekend. First I just tried to set the IP of usb0 to a 192.168.3.3, but that created a second interface with name usb0, it didn't replace the old one! So in the end I just commented out ModalAI's lines about setting the IP and added ```ip link set usb0 down``` instead. I needed to make the service restart on fail, as it runs before usb0 appears, which causes it to fail. step by step: 1) edit ```/usr/bin/voxl-static-ip``` Comment out the last two lines and add one to look like this: ``` # set new IP #sudo ifconfig $INTERFACE $LOCAL_IP netmask $NETMASK #sudo route add default gw $ROUTER_IP $INTERFACE ip link set usb0 down ``` 2) edit ```/etc/systemd/system/voxl-static-ip.service``` Add two lines to make the [Service] section look like this: ``` [Service] ExecStart=/usr/bin/voxl-static-ip Restart=on-failure RestartSec=1s ``` 3) -Profit ## Reply by tom (ModalAI staff) · 2022-10-17 16:55:06 UTC @Patrick-Hinchey I'm not entirely sure where `usb0` is coming from and why it's enumerating. From what I can tell, all you have connected hardware-wise is the WiFi adapter (`wlan0`) and the LTE modem (`wwan0`), is that correct? ## Reply by Patrick Hinchey · 2022-10-19 00:10:30 UTC (in reply to tom) @tom yep, the LTE modem (```wwan0```) is plugged into J3 and the Alfa WiFi module (```wlan0```) is plugged into the LTE modem's USB breakout. I don't understand why ```usb0``` would be there either - at first I thought it the adb but adb continues to work even when I set ```usb0``` down. FWIW, I bought multiple units, and so far both the ones I've tried enumerate ```usb0``` on both platform releases 1.1 and 1.3 ## Reply by tom (ModalAI staff) · 2022-10-19 16:27:30 UTC @Patrick-Hinchey From what I can see, it looks like it's a bug in `voxl-modem` where `usb0` is being pulled up when it shouldn't be. I'll have to dig into this a bit to find root cause. It is somewhere in `/usr/bin/voxl-modem-start.sh` that is doing it. This is the modem enumeration script that runs at boot. You can see the systemd service file at `/etc/systemd/system/voxl-modem.service`. ## Reply by Patrick Hinchey · 2022-10-26 03:03:20 UTC Interesting! I'll keep watching this thread for when you commit a proper fix in voxl-modem. For the meantime, my hack is working for me. Thanks!