DNS Forwarders

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Christopher Aaron Farnfield

Could any one tell me what is DNS Forwarders, or where to
find the information about it?
 
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Christopher Aaron Farnfield said:
Could any one tell me what is DNS Forwarders, or where to
find the information about it?
Click to expand...

A forwarder "forwards" queries for zones that the DNS server is not
authorative for. Authorative for a zone means that the zone (domain name)
has been created on your DNS server. If your DNS query receives a query for
a zone that it's authorative for, it can give the answer right away from
it's own records. If it does not have the answer, it will try to find it
some other way, either thru a Forwarder or the Root Hints. The Root Hints
can be viewed under the Root Hints tab in DNS properties. Using a forwarder
is much more efficient on your DNS server then using the Root Hints, since
it "forwards" the query out to another DNS server to provide the answer. An
example of a DNS server address that you would forward to would be your
ISP's DNS server.

How to configure a Forwarder. Look below Step 3 in this article. If the
op[tion to forward is grayed out, delete the Root zone, and close and
re-open the DNS console and try again. Both of these steps are shown how to
in this article:
http://support.microsoft.com/?id=300202

You can find more information about forwarding and many other features of
DNS at this site:
www.microsoft.com/dns

Here's a complete training CD on how DNS and it's features work:
http://support.microsoft.com/default.aspx?scid=kb;en-us;330511

--
Regards,
Ace

Please direct all replies to the newsgroup so all can benefit.

Ace Fekay, MCSE 2000, MCSE+I, MCSA, MCT, MVP
Microsoft Windows MVP - Active Directory
 
Christopher Aaron Farnfield said:
Could any one tell me what is DNS Forwarders, or where to
find the information about it?
Click to expand...

It's easiest to explain with an example -- the most common example
you will read about here.

Suppose you have an internal DNS system, maybe even running on
your DCs and you either don't want these internal DNS servers (DCs)
to visit the entire Internet to resolve names (dangerous!) or you cannot
have them do that because of a firewall between them and the Internet.

Internal DNS -- clients configured to use it. Internal names resolve
just fine, but what about external names on the Internet?

This internal DNS can't (or shouldn't) go out there.

We set its "Forwarders" tab on the DNS server properties to "point to"
another DNS server which CAN access the entire Internet namespace
from the root DNS servers down.

This externally active DNS server is called a Forwarder. It's kind of funny
that this DNS server doesn't even know that it "is a" forwarder.

It is very common for you to forward to your ISP's DNS server or perhaps
to your Gateway/Firewall/NAT/router to the Internet if it can run a DNS
server.

This last idea, forwarding to a DNS server on the firewall/router serves an
additional purpose: It consolidates the external cache of names resolved so
that internal DNS servers don't have to repeat the same requests and it
thereby "protects the WAN" bandwidth or speeds up resolution.

So, what's a forwarder? It's just another DNS server that your DNS server
uses to help it do the actual name resolution for names the internal server
doesn't
know.

The clients and the forwarder don't even need to know that you are using the
"forwarder." Only the internal DNS servers set this up.
 
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