Originally Posted by skellam

As stated above, if you are using DHCP, the router should obtain the DNS settings from the upstream provider (whether that is the DSL or cable provider). If they are not auto assigned then you will need to contact whoever provides your internet service to obtain them. Most ISP's have a server that provides DNS services. However, there is no rule that you have to use the ISP's DNS server. One option you could use is to try OpenDNS which provides DNS services and also the added bonus of free filtering of websites. They have detailed instructions for setting your routers DNS setting here.