Internal & external DNS setup with firewall

[Jonathan de Boyne Pollard]

THY> So, which one should I set ?

Your internal proxy DNS server.

THY> Should I need the different domain name between external & internal ?

No, unless all of the following are true:

    * You have a Microsoft Active Directory domain by that same name.

    * You _require_ <URL:http://example.com./> to work, for your 
internal machines, as well as <URL:http://www.example.com./>.

    * You are _not_ running content HTTP servers, capable of serving up 
the requisite web site, on _all_ of your domain controllers.

Other issues are merely exercises in setting up "split horizon" DNS 
service properly and actually populating one's internal content DNS 
server's database with the requisite data.

One of these days, Microsoft, Netscape, and others will pull their 
collective fingers out, implement "SRV" resource record set lookup in 
their web browsers, and even the aforementioned combination of factors 
will not require that one employ two different domain names.

THY> Can I nslookup firewall that will give two IP result ?

If you decide to publish those data, yes.

THY> Did the local DNS [server] need the root.cache file ?

If you are configuring it to perform query resolution itself, yes.