I've recently changed the DNS settings on my latest generation Airport Extreme from their default values to Google DNS. My reason was obvious, I want all of my devices connected to my network be able to use Google DNS without me configuring Google DNS on every single one of them.

After doing so, I still see my default DNS values on my Airport Express, which extends my network, and all of my devices. Is this behaviour right? Does all of my devices use Google DNS as a result but not show it or is there something wrong?

Update

I've a fiber connection of 50 Mb/s at my home. The fiber cable coming into my apartment is connected to a box provided by my ISP which resolves getting fiber to my home. From that box, a LAN cable goes out to the modem/router box provided by my ISP. That box only serves me as a modem and a wired router since I've disabled it's WLAN functionality by it's dedicated button to disable WLAN. And another LAN cable out of the modem/router box goes out to my AirPort Extreme for providing me with wireless connectivity throughout my apartment along with my Airport Express extending Airport Extreme's broadcast.