Windows 2000 DNS Question

I currently have 12 DNS servers spreaded across the country all with the connection to the internet going through a central location via a PRN.  These DNS servers all have an AD integrated forward lookup zone.

The way I understand name resolution is working now is this. Client 1 is at location 1.  If client 1 goes to the DNS server at location 1 performs a recursive query to the root internet servers going down until it hits  Client 2 who is also at location 1 does the same thing only this time the website is resolved by using the cache located on the DNS server at location 1.  Now if clients at location 2 do the same thing, it first has to be resolved by an internet root server again, then cached on the DNS server at the second location.

Using this logic (please correct me if I am wrong in how it is working) I could do this: Add a forwarder on each branch location to to my DNS server at the central location.  On the DNS server at the central location, either add a forwarder to my ISP's DNS server or just let it resolve by using root hints.  Now instead of each individual DNS server having to resolve and then cache the queries, it will simply forward the request to the central DNS server which has the query in its cache and resolve it without having to go outside of my network.

Does this make sense and will it work?
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it makes sense to me, it will however slow things down if your "main" dns server doesn't have the zone cached already since intead of going from client>local dns server>root hint

it will now have to go from client>local dns server>main dns server>root dns server or ISP's dns server

as you can see, if the zone isn't cached, you have just created an extra step.

are you experiencing slow DNS times?  is that why you are thinking of doing this?  A more standard setup would just be to point all of the local dns servers to a few of your ISP's dns server since the root hint servers are often busy.

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I agree with mikeleebrla about pointing your local DNS servers to the ISPs instead of pointing them to your central server.

bwalker1Author Commented:
My DNS time are not slow, I was thinking I could put less load on my central internet connection if I did this.  My DNS servers have to go across two WAN links as it is to go out on the internet themselves (one to the main site and out to the internet from there.) I was thinking if they could resolve the query without having to out to the internet a second time, I could save a lot of total bandwidth.

What do you think?  Will it really save much bandwidth or should I just leave it as-is?  
Leandro IaconoSenior Premier Field EngineerCommented:
Well, you could always try it out. As you put it out it should work perfectly... and you'll only have the dns servers query your central dns once, until they cache the cached entry from central dns.... right?

I would test it out, and see what happens.

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Windows 2000

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