Check different lan ports on router. Some of them may go through NAT, some without NAT.
It looks like under Network/Broadband settings/Connection Type.
"Bridge" setting - would pass internet to lan ports without NAT and
"Route" setting - would make them go through NAT.
Wifi would go through NAT always, you want lan ports go through NAT too.
Yeah, I checked the router's setting and the instruction manual, there's nothing there regarding wlan isolation. I've called my ISP but the call center agents aren't exactly wiz kids.
*edit
My router is a FiberHome AN5506-04-FA supplied by my ISP.
Check different lan ports on router. Some of them may go through NAT, some without NAT.
It looks like under Network/Broadband settings/Connection Type.
"Bridge" setting - would pass internet to lan ports without NAT and
"Route" setting - would make them go through NAT.
Wifi would go through NAT always, you want lan ports go through NAT too.