Why Is My Internet Working! :S

(schematic available at [url])

I am building a new network here, and I have built all the infrastructure servers and built the firewall server (as well as connected it to the internet), just for testing, I have allowed all traffic to anywhere.

Now, the firewall is set up so that it has the DNS for the router (192.168.0.1) on the internet NIC, and on the internal NIC it has DNS set up as 10.0.0.2 and 10.0.0.3 (FYI, DMZ is blank, but the mahcines on DMZ have the same .2 & .3 set)

I can understand why internet works from the firewall machine as it is getting DNS addresses from the router, however I loged on to INTERNAL1 (the primary infrastructure server), which for DNS, only has itself (and the .3 machine as backup), and I can get full internet... It fully 100% works.

I can not understand this! the dns server that it has does not have ANY fowarders configured, however the websites I visited appeared in the cache just fine.

So, My question is, how on earth was I able to connect to the internet... it just makes no sense to me