I have this problem for years, either the V1 and V2 routers

We have 2 WANS and 3 LANS

LAN1 -> 10.10.0.0 (Servers) DCHP OFF

LAN2 -> 192.168.0.0 (Computers) DHCP ON

LAN3 -> 174.162.40.0 (Routers free internet for clients) DHCP OFF

The routers are Mercusys MR50G and they are connected by WAN port.

The LAN1 is connected direct to the server, so don't count it.

LAN2 and LAN3 are connected to the Switch. (TP-Link Business switch)

The routers are connected to theses Switch all in the WAN port.

The routers in the LAN2 network (192.168.0.0) got internet

The routers in the LAN3 network (174.162.0.0) don't get internet

no matter what I do.

The only way to get the routers working with internet is creating a static route

174.162.40.0/24 > 192.168.0.1

The problem is, it in fact should not be needed, and is not secure doing that because I somehow link my free internet for clients to my internal network.

TP-Link never fixed this, and I have I thread opened years ago, they said there's something wrong, but didn't fix anything