From: John Beckett 

I just tried this on an NT4 SP6 computer. I was able to add up to a total
of three DNS servers. At three, the Add button is disabled.

I haven't noticed this before, but frankly it sounds reasonable to me
(perhaps you managed to enter four using some older service pack version).

I have had my confidence in how DNS lookups shaken a little by W2000 which
does things differently than NT4, but here is how computers used to work
(i.e. I believe NT4 works like this):

You use an NT4 computer to access host whatever.somewhere.com. Your
computer asks its first DNS server for the IP. If that server times out (no
response within a few seconds), your computer asks the second DNS server.
Likewise, if that one times out, the third is asked.

So, if your Internet connection was dead and you had four+ DNS servers,
there could be quite a delay before you got a response that it wasn't
working.

With NT4 if a DNS server replies and says "the name you are looking up
does not exist", your computer believes it and will NOT ask the other
DNS servers. The alternate DNS servers are backups in case one is dead.
They are supposed to hold the SAME database of names/IPs.

However, since W2000 there appears to be a difference which I've never got
around to investigating. Also, I've never seen any documentation - if
someone has a reference, please tell me.

In W2000 it appears that your computer WILL ask the second DNS server if
the first one says the name does not exist.

Frankly, there should be no reason to have more than three DNS servers.

John

Randall Parker 
wrote in message news::
> On two different NT4 Sp6a machines with the latest fixes installed I go into
TCP/IP
> Properties and the DNS tab. THe DNS Service Search order control has the
Add.. button
> grayed out on both machines. Why is that?
>
> One machine has 3 existing DNS servers listed and the other has 4. I added
them a
> long time ago but want to add a new one. Any idea how to do that?
>

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