If you're referring to DHCP passing on multiple DNS server addies to the clients, then you will have to do the following:
1) Disable DNS relay in the Network Settings section, and
2) Enter Primary and Secondary DNS addies in the Internet Section. If you don't enter the addies manuallym then the router will pass on your ISPs DNS addies. It will still be two (and not three) addies that the clients will get.
Hope this helps.