3 seperate networks - how do i get from one to the other ?

Hello,

We have set up 3 LAN networks

ETH1 = WAN

ETH2 = UPSTAIRS 192.168.2.x gateway 192.168.2.1 dhcp

ETH3 = WIFI 192.168.3.x gateway 192.168.3.1 dhcp

EHT4 NOT USED YET

ETH5 = DIRECT-LAN-PC 192.168.1.x gateway 192.168.1.1 dhcp

What do i need for settings to be able to get from ETH5 to ETH2.

I tried adding a bridge between ETH5 and ETH2 but then dhcp turns red. i assume its because they are different.

Please advise, i would like to monitor the traffic from WAN to ETH2 and ETH3 and ETH5 and still be able to copy things over to a machine in the ETH2 network.

Thanks in advance,

Megatik