Considering only the Wireless aspect of a network, is there any security advantage of creating a separate SSID for guest, rather than simply setting option isolate
to my lan?
I am not aware of any. Given that I am ok using the same dns resolver for guest and lan (I don't see much value in differentiating), I am tempted to simply use option isolate, and share my lan's wifi key with my guest. Does that reduce the security?