Recently my ISP changed my network so that my Apple Airport Extreme has to connect to the ISP router rather than directly to WAN. So, I had to put my Airport Extreme in 'bridge mode.' The consequence is, it seems, that the guest network feature does not work. Now, what I can do is to instead have my guests connect directly to my ISP router (which also has WiFi). My question: is that as secure as guest network? So that they cannot connect to any devices on the airport extreme?