My Flint 2 runs fine. Usual business: routing the Internet from ISP, getting 192.168.0.10 from ISP's modem DHCP and serving local network under 192.168.8.0/24.
Unfortunately, there are problems with ISP so in the meantime I switched back on an old B535-333 4G router and plugged it to Ethernet 2 (switched from LAN to WAN in Network port management -> the manual needs to be updated). The 4G router gives 192.168.9.101 to eth2.
ISP's modem is still plugged to Ethernet 1 so that it takes over when ISP sorts out their mess.
I made sure the 4G router"s WAN port is pingable so the Flint 2 can see it. Then, I thought it would be enough to enable Multiwan failover mode and everything would be fine but it would have been too easy.
Too bad, I now get the following error
Guest subnet is in conflict with the WAN subnet, Please Change Guest Subnet to a different address.
on Ethernet 2's tab.
Any clue on what I do wrong here?