There SHOULDNT be.
I would have to check when i get home.. (at work right now).
But the devices that i did have with a dynamic IP assigned by the CGN3's DHCP server
(most are static), last i checked, were assigned a DNS relay address of 192.168.0.1 (in my case) for the DNS server, and used that as a relay to the two stored in the CGN3.
(the static ones, use the GOOGLE DNS, and not the rogers ones)