New Shaw hookup; curious about provided Cisco DPC3825

Hey guys! Forgive me if I show ignorance here with this question: I was given the Cisco DPC3825 for a new 20Mb hookup (promotion right now). In hooking things up to my network, and replacing my trusty Netgear wireless router with this Cisco (I was on Telus, with just a plain old Speedtouch modem with no wifi), I find that I can assign static IP's and gateway to devices internally, as I am used to, but assigning the static DNS server to the Cisco IP (192.168.1.1) does not work? So, example would be for Device 1: IP = 192.168.1.2 Subnet = 255.255.255.0 Gateway = 192.168.1.1 (Cisco modem/router) DNS = 192.168.1.1 (does not work!) In fact, what I have had to do is look at the Shaw assigned DNS servers within the Cisco interface, and assign those DNS servers manually to each internal network device if I want it to access the internet... Is it normal that this Cisco modem/router does not smoothly respond to DNS requests sent to it by devices on its internal IP? Again, every single router/modem I have ever used, whether Shaw or Telus or whatever...has always been just fine with assigning devices connected to it its internal IP as DNS, and thereafter DNS resolves fine on those devices... Help me out here fellas...am I on drugs or what?