Hello david8,
If you are using a cable/DSL modem, then it is likely that your DNS server address is 192.168.1.2. If not, then it is likely that the DNS is fed from upstream automatically...but that all depends on how your IP is/was set-up.
You can verify your DNS easily by Run cmd.exe, in the window type ipconfig /all (space between g and /), then hit enter.
You should find a line item "DNS Servers...."
By the way, if you're using ("behind") any type of cable/DSL/NAT router, it enforces a minimum level of protection in that it monitors packets and only allows those that are initiated by your system. In other words, most importantly, it will only allow in-bound packets that are in response to a connection initiated by your system. So, in some respects, a firewall will be superfluous (not necessary).
That's OK though...as I use a NAT router and insist on using a firewall behind it so that I can be alerted when an app makes an outbound connection. It's a smart security measure in its own right as a malicious program can initiate an outbound connection, but an ordinary NAT router doesn't know that its malicious. So since the connection was initiated by your system, the NAT router is going to allow any in-bound packets...which can be really Bad News!
If you use Comodo secure DNS, then you will be quickly disappointed.
I think many users instead choose Norton's secure DNS. I, myself, do not bother with it, but that is solely my choice. A secure DNS theoretically is supposed to add a solid additional layer of protection. From what I see, Web-Of-Trust (WOR) or an equivalent web filter does essentially the same, or better.
Even the built-in Internet Explorer smart screen does a better job than Comodo secure DNS. The same applies to the Chrome and FireFox web filters.