@BigD 

 

You can take a cable from the switch and plug into the WAN on the TL-ER5120, but why you still want to take a cable from the switch and plug into the LAN on the ER5120? 

I think you can remove the cable between the LAN and the switch. Then the clients in the LAN of ER5120 still can access the internet.

@Andone 

 

Thanks, not sure if i have explained it very well. I have both clients and broadband connections on a single cable from another building that plugs into my switch. I want to have these broadband connections managed by the ER5120 so imagine i need to plug them into a WAN port on the ER5120, so would need a cable for each broadband connection plugged from switch into a WAN port on the ER5120.

I got your meaning. You client and broadband is from the same cable connected to the switch. I think it cannot meet your demand. Still need to isolate the clients and broadband.