Redundancy for multiple lossy connections

Technical Support for Routers
1

Hi,

I'm having to install a LTE/NR based internet connection at a location which unfortunately is a rather unstable environment for radio. Meaning that a single LTE/NR connection will cut out multiple times per day. This happens with all telco's to some degree, though not at the same time. So I'd like to use a Spitz AX and combine multiple LTE/NR connections for redundancy.

Now, the end goal is to be able to hold video calls over IP - without losing audio/video for more than a few seconds if one of the radios goes down. Perhaps this sounds unachievable, however I believe that it can be done - with typical Linux at least it can. Basically, it requires the following:

  • Both connections must remain online/ready to go. So no standby sim, rather a single sim in the router plus an extra phone or external modem (via usb or WAN interface).
  • Switching between the two should happen quick. Pings are generally low, so once the first pings go beyond 250ms I'd want an immediate switch.
  • I'd want the public-internet facing IP address to remain the same when switching between the two LTE connections. This requires a tunnel from the router to an external server (which is online 24/7). Even if the tunnel switches between the two LTE connections, the tunneled traffic will still always originate from the same IP (The IP of the external server). This allows a switch between LTE connections to take place without internet-connections to be reset. A few packets lost, yes, but no reconnect.

I've tested WG client on a linux box and it is capable of keeping tunneled connections alive while switching between internet uplinks. The setup is rather simple:

  • Ping-test-IP's for telco1 are statically routed over the telco1 interface
  • Ping-test-IP's for telco2 are statically routed over the telco2 interface
  • Wiregard server IP is routed over either telco1/telco2 interface depending on which of those is considered the healthiest (determined using ping tests). This causes all wiregard packets to flow over the best telco connection, and adjusting routes between telco1/telco2 will immediately take effect as it's simply UDP traffic.
  • Everything else is routed over the WG interface (i.e. through the WG tunnel).

The above works on Linux. However, the trick here is to determine if it would on the GlInet device.

I have not purchased the Spitz device yet, however would like to see if members on here that have experience with this ecosystem would consider this feasible.

One thing I am wondering about is how much control we have over the WG config. For instance can I configure WG to not control routes, but allow my script to set those according to the above?

Another thing is that I would require both WAN connections to be "equal" from a metrics perspective, and adjust the ones used simply by adjusting routes.

Has anybody attempted setting something like this up previously?

2

I would say it should be possible by routing all traffic through a WireGuard VPN tunnel to your external server. Maybe even AstroWarp (currently in beta) would solve this.

But please keep in mind that none of the GL routers can use 2 SIM cards simultaneously. Switching directly won't happen, and I would even say that high ping times are nothing that would initiate a switch between the lines.

Maybe you should go with plain OpenWrt instead of the GL firmware. It makes it easier to adjust everything you need without having issues because some consumer scripts of GL might revert changes.

3

Thanks admon. AstroWarp looks interesting.

I'm aware of the dual-sim limitations. Therefore I was planning to use one simcard in the router, and the other in an external modem (or phone through usb tethering). This would give me two 'hot' interfaces if I understand correctly (The internal modem, and a Tethering interface)?

Would using only OpenWrt typically still support the NR modem and the fancy options like band or cell lock (Which are quite powerful for these situations with unstable connections)? I'm aware most of those can be done through AT commands but, unless I'm mistaken, that also requires to be re-done after each reboot - which would be a bit of a pain.

Thanks!

4

Correct. 2 interfaces: Modem and USB tethering.

As you mentioned, OpenWRT also support the band/cell lock via the AT commands, and it is not as intuitive as the GL firmware.

5

This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.