2 separate WANs and LANs on a single OpenWrt router

Hi, I have 2 different networks each with its own WAN and LAN subnets and I am trying to use a single multi-ports OpenWRT router to house both networks. I have gotten almost everything figured out but could not find a way to define the default gateway to each network individually. To give a clearer example:

eth0: WAN1 IP address: 12.34.56.78 (dhcp assigned by provider1)
eht1: LAN1 IP address: 192.168.1.1 (static, dhcp server enabled in OpenWRT)
eth4: WAN2 IP address: 87.65.43.21 (dhcp assigned by provider2)
eth5: LAN2 IP address: 192.168.2.1 (static, dhcp server enabled in OpenWRT)

How can I set all traffic on LAN1 gateway pointing to WAN1, and LAN2 gateway pointing to WAN2? I am not trying to do any load balancing or fail over from WAN1 to WAN2, just 2 distinct networks.

Can anyone help? Thanks!

You can implement policy-based routing (PBR) using routing rules in UCI, or use a package which supports PBR.

In the first case you configure ip4table (and ip6table) on each WAN interface and then add one rule for each LAN which selects the correct table.

Thanks! Let me try PBR now, never use it before.