Setting FQDN in network with only some public-facing servers
 

What is the recommended policy regarding naming computers on a network with some public-facing servers? DNS for the public-facing servers is resolved by a third-party DNS provider. For example:

www.example.dynamicdnsprovider.org
mail.example.dynamicdnsprovider.org

What happens if I give the same FQDN to the private machines as well (minus the hostname itself, of course)?

For example:

desktop1.example.dynamicdnsprovider.org
desktop2.example.dynamicdnsprovider.org
desktop3.example.dynamicdnsprovider.org

I want to run a local caching name server to resolve these internal names. Would it be considered better policy to give them a FQDN of lan.local instead? I don't want DNS requests for the private network to leak out onto the Internet.

Most places will use a separate domain for internal use like in.company.com, you can prevent information leakage by using 'views' in bind.

Thanks. Google doesn't always provide an authoritative answer to these things. I was in the habit of using lan.local for private networks, and didn't know what to do when I started putting public servers up; I now understand it's better to use a subdomain of a registered domain. For example:

desktop1.lan.example.dynamicdnsprovider.org
desktop2.lan.example.dynamicdnsprovider.org
desktop3.lan.example.dynamicdnsprovider.org

instead of

desktop1.lan.local
desktop2.lan.local
desktop3.lan.local

I'll read up about views now.