In case I have not made myself clear I will try this one last time, then I am going to hunt Lycan down because this is getting ridiculous.
THIS SWITCH'S LAN PORTS ARE ON AN UNMANAGED SWITCH. IT IS NOT POSSIBLE TO CREATE AN ISOLATED INTERFACE ON AN UNMANAGED SWITCH. IMPOSSIBLE. THERE IS NO FEATURE REQUEST TO ELEVATE AS IT WOULD TAKE ANOTHER PHYSICAL INTERFACE TO PERFORM AS YOU REQUEST. I AM GOING TO ADD ANOTHER IMPOSSIBLE FOR CLARITY.
If you want a DMZ interface buy an firewall with a DMZ interface instead of a product designed to forward unspecified traffic to a LAN host as a last ditch effort for troubleshooting and setting up server software you know nothing about.
I mentioned the guest network feature because you asked me about it.
Every consumer level router (which is what this product is) that I have ever seen has this very feature and refers to it as DMZ, so the "but all my friends are doing it..." argument is not only valid, its as good as law.
While we are drumming up things we are liable for telling every customer should we add a list of every piece of network exploit software ever written in the manual. Perhaps we should require that they understand firewall theory to buy our product. Or better yet, we have to warn them that they are "bad people" on the other side of that wire.
You purchased the wrong product for your purposes, return it and buy a product that does what you require instead of expecting your consumer grade equipment to match your ridiculous expectations. The number for Customer Service is 1 800 326 1688 ext. 6314, they can figure out who I am based on my handle.