Mwan3: fail-over to alternate gateway reachable locally by static ip address

Installing and Using OpenWrt
1

[TL;DR I need to fail-over from my "wan" port to another (fixed, known) ip address I can reach locally as an internet gateway]

Hi guys.

I have two internet uplinks in my house. My OpenWrt router is connected to my main internet uplink, which is a fiber line. The WAN port of my router is connected to the optical network terminator (ONT), which is basically just a media converter between fiber and ethernet.

The second uplink is a DSL line. Sadly, I don't have a DSL modem that simply could be put into "bridge" mode, but I have a FRITZ!Box provided by my internet provider that integrates the DSL modem.

I have now connected a LAN port of the FRITZ!Box to my OpenWrt router (created an interface for one of my OpenWrt router's lan ports, assigned a static IP that's part of the FRITZ!Box' lan), like this. I then created a static route on the FRITZ!Box.

Now I "just" have to configure mwan3 to fail-over from OpenWrt's "wan" interface to the FRITZ!Box's gateway address in its lan (192.168.178.1), that I can now also reach from my OpenWrt lan.

I also have issues imagining how the setup would look like with regards to IPv6. The FRITZ!Box uplink sadly doesn't have IPv6. So when a fail-over would have to be performed, because my fiber line is down, then I would only have IPv4 connectivity. I believe from the wiki that mwan3 would be able to handle such scenarios? Define separate IPv4 and IPv6 policies/rules using failover for IPv4, and for IPv6 just reject?

Thanks in advance for sharing any helpful thoughts or advice.

Kind regards,

Ralf

2

(For reference:)

I've configured a static route on the FRITZ!Box as follows:

192.168.2.0/255.255.255.0 via 192.168.2.2

where 192.168.2.0 is my LAN on OpenWrt, and 192.168.2.2 refers to my OpenWrt router's LAN port that connects it with the FRITZ!Box's lan.

3

Which FB model is it? Quite a few are well supported by OpenWrt ...

4

Hi Andy.

Thanks for your interest and response.

Sorry, I missed to mention that the FRITZ!Box is "virgin". I don't want to reflash it, because I'm not owning it, it's being owned by my ISP.

(Also, by reflashing it I would lose its (native) capability to act as a SIP gateway and to drive the DECT access point. The former I could probably "emulate" by Asterisk or something similar, but the DECT functionality would be lost, right?)

So we're talking about a FRITZ!Box with OEM firmware.

My question is really "just" (mainly?) one related to routing using mwan3, I believe.