Hi,
Here's another solution:
1. Reset your router to defaults so no configurations would interfere with this new set-up.
2. After that go to your Network > VLAN and create a new VLAN ID (3), but do not tag or untag any ports, type only the name and that's it. Save.
3. Go to your Network > Interfaces and create a new interface - named something like LAN2.
3.1 Give it Static protocol.
3.2 Enable DHCP server
3.3 IPv4 address 192.168.3.1
3.4 IPv4 netmask 255.255.255.0
3.5 Save.
4. Go back to editing your new LAN2 interface and head to Physical settings
4.1. Enable Bridge Interfaces
4.2. Select eth0.3 in the list as your interface and nothing elseю
4.3 Go to Firewall settings and select LAN zone as your new interface firewall zone.
4.4 Save.
5.Head over to Routing > Advanced Static Routes.
5.1 Add new routing table with ID 300 and any name, e.g lantraffic.
5.2 Go to your table editing page (pencil icon on the right side).
5.3 Add Static IPV4 Route with the interface you wish to assign. In this case, I want to separate the mobile connection:
Configure it like this and save.
5.4 Go back to the Advanced Static Routes page and add Routing rule with your new LAN interface as incoming one:
5.5 Save.
6. Now we will go to CLI and do a small change in the network configuration file.
6.1 Login to your CLI and execute vi /etc/config/network, once you're in the document press letter i on your keyboard to start editing the file.
6.2 Find something like this interface and add the line option ip4table '300':
After you're done editing press ESC on your keyboard and type :wq to quit editing and save.
Execute /etc/init.d/network restart to commit your changes.
7. Finally go back to your Network > VLAN configuration in WebUI and change your wanted port from the first ID, from Untagged to OFF.
And then give it Untagged on ID: 3.
After this save your configuration and you should be able to see that traffic is coming from a different source for that port exactly.
EB.