DNS!!?

[yenchiung]

Excuse me!!!
Why should we establish 2 DNS zones in one company?
For security reasons?
How could wu setup 2 DNS zones with Mail Server(Exchange 2000)?
One Domain Name is true for outside, the other just for inside!!?
Thanks a lot ^^.

[milwater]

The resaon why u use 2 DNS zone is just because for the security that hackers could't easily know about the network structure of your company. Once u use only 1 zone, the inside and outside zone are the same, all PCs and Servers are easily to be attacked. However, if u use 1 zone for outside and 1 zone for inside, even hackers break into the outside DNS zone, it still get other defense for inside network - the most important network area.
Please refer to the key words for search engine:Mirror Site, DMZ