DNS: assistance please

You have the right idea. The correct way to accomplish this is below...

- nslookup <press enter>
- set type=NS <press enter>
- rootdomain.com <press enter>

When you are using the root domain it will give you a list of all DNS servers in the root domain and child domains as well.

Will.

Is there a way to export this to a file

Just right click select Mark, highlight what you want to copy and <press enter>. Open Notepad and then paste the contents in there.

Will.

There are 300+ entries

That is still manageable. All you need to do is increase your cmd prompt window height. From there it will give you more space vertically. You increase this by doing the following...
- open cmd
- top left corner, select properties
- select layout tab
- under "Screen Buffer Size"  increase the height to like 3000

That will allow you to have plenty of scrolling space. Then proceed to copy.

Will.

One thing I noticed, in 1 forest it displays all the dns servers in all the child domains, and in the main production forest it displays only the dns servers in root domain. Any ideas.
I used the same commands as you had listed.

May be the Dns zone of the root domain is only in root domain wide and not forest wide and in the Dev forest zone that works, the devzone  is replicated forest wide to all dns servers