Question

I still do not really understand the mechanism of failover between both LTE connections: If I have setup failover between mob1s1a1 and mob2s1a1 (status on and active) and the rules section is completely empty, should failover work properly or do I have to setup a special rule (or even a default) rule additionally to have a proper failover functionality between both modems?

If this is the case, that I need at least a default rule, what would be the parameters for failover the whole internet traffic in case the primary modem fails and the X12 switches to the secondary modem?

Answer 1

Hi, default rule shouldn't be missing. Easiest way to recover it would be to reset router to factory defaults and set it up from scratch, but if you'd like to avoid that then you could try to reconfigure default rule similar to this:

https://wiki.teltonika-networks.com/view/RUTX12_Failover#Rules

When it comes to mobile failover in general, RUTX12 is a bit of a unique case, because technically the failover should happen by default if primary mobile interface goes offline. Now when it comes to which default route would be picked by the router - that will depend on metric of both mobile interfaces (lower metric = better interface [default route]). You can test this by running a simple ping test from your PC/smartphone and removing SIM1 (assuming that's the SIM slot of your primary mobile interface).

Still, failover service will help to determine whether internet connectivity is actually gone by sending ping (icmp-echo) packets towards specified host and the failover should occur much smoother.

Answer 2

Should this work as rule for failover between primary and secondary modem?

Comments

I believe so. Default config also has destination address field "0.0.0.0/0" filled out (if I recall correctly), but besides that configuration seems pretty much identical. Try testing it by removing SIM1 and see if you still have internet connectivity via secondary modem after a minute or two.

Answer 3

I would rather like to technically understand what exactly "Source address" and "Destination address" means in this regards. The manual is not very precise in taht point.

Comments

It's as simple as it sounds - this rule will match only when src/dst IP address is matched (if specified) and specific policy will be applied. If rule is not matched, another rule will be looked at by the router, until there are no more rules left. This concept is similar to iptables firewall rules (which is, in fact, utilized by failover/load balancing package). Using these rules & policies you may redirect and manipulate routing of packets, depending specifically on source and/or destination IP addresses.

As an example, if your PC, which has an IP address of 192.168.1.123, generates an IP packet towards host 1.2.3.4, a [very specific] rule would be matched if source/destination addresses were configured as follows:

• Source address - 192.168.1.123
• Destination address - 1.2.3.4

If these characteristics in an IP packet match, then some designated policy will be applied for that packet.

Failover/load balancing service utilizes mwan3 package. It's documented extensively on OpenWRT wiki, if details interest you:

https://openwrt.org/docs/guide-user/network/wan/multiwan/mwan3

Answer 4

Hello,

The way failover works, at least with default settings, is by periodically sending ping requests to a pre-configured host(s). If the router receives replies, it considers interface to be online. If, however, the device fails to receive a set number of reply packets, it considers that there are connectivity issues on this link and the next WAN interface online with the lowest metric is chosen to forward traffic to the internet. The default options are provided below.  

They can be modified according to your needs, in case you want to have a different or multiple end points to test connectivity over specific interface.

In addition, I suggest to edit settings for each failover interface by pressing on pencil icon and append option Flush connections on with Connected and Disconnected settings. This will force already established connections to be rerouted through the currently used interface, in case connection is disrupted, without waiting until currently established connections time out.

The rules are more oriented for cases, where you want certain subnets or LAN devices or traffic originating from specific hosts to be routed through different interfaces than the current main setup.

Best regards,

Answer 5

Thank you very much, it is working as expected.