I have a NETGEAR router WNDR3700 with OpenWRT v18.06.2 installed.
It's configured with mwan3 to load-balance my 2 internet connections.
I have connected the first ISP Modem/Router (Modem A) to the regular WAN port ("wan" interface) and the second one (Modem B) with the wanb interface (LAN-1 physical port). Both the ISP modems are having DHCP enabled. All works well till now, with "wan" and "wanb" interfaces functioning perfectly fine distributing the load between the two ISP routers/modems.
But when I swap these connections, i.e connecting the first Modem (Modem A) to "wanb" and the second one (Modem B) to "wan", I see that the wanb interface is disabled and non-functional. It makes the connection in the regular wan port (wan) only functional.
What could be the problem? Any help is appreciated.