Hi! I have a Mikrotik RouterBoard 750 and the scenario is this:
1- Connected to eth1, ISP that gives me IP: 172.56.7.9 (as a gateway, it is only for the example).
2- Connected to eth2, work intranet IP: 10.20.3.2 (as gateway, it is only for the example).
3- Connected to eth3, LAN network with IP: 192.168.5.xx (gateway 192.168.5.1, it is only for the example).

Once that is done I would like to achieve:
1- That if any user on the LAN wants to see YouTube, Facebook, newspapers, etc. Automatically exit on eth1.
2- If any user on the LAN wants to use a resource on the intranet, they should automatically exit through eth2.

I'm sure some genius who is in this forum will know how to guide me !!!

Solution A: Routing
Just Set-Up your Mikrotik-Router exactly like you described.
Make sure only ether1 (ISP) as a "default route".
Then,
If your Client want to access the internet, it will go to your default Gateway (aka ISP1)
If you want to access Work resources (10.20.X.X) if will automaticaly go thru your Work-Network (ether2)


Solution B: Mangel
With the help of the Mirkotik mangel funktion.
For exemple, you can "Mark" different Connections as "Work" or "Privat"
After Tagging, you can assign a Routing-Table for the different Connections.

Hi ConnyMercier. Good day!
I will follow what you tell me and comment on anything here. Thanks!