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duplicate name exists on network??

Posted on 2006-05-19
Medium Priority
Last Modified: 2012-08-13
haveing a little name resolution issue on a small network..  no domain controllers.  

Migrating contents of windows 2k (Atlas) file server to an existing 2k3 (titan) file server.   Both machine have existed on network for some time now..

I have a local DNS entry for Titan ( A Record

copied data from Atlas to Titan, recreated the shares, permissions, etc..  

there are some apps in the office that point to \\atlas\share  for data   so I wanted to keep the "atlas" name around and just point it to the new IP where the shares now exist...

Created and A record for Atlas that points to the IP of Titan (

turned the old 2k server off.  

Now when I try to map a drive to \\atlas\share or  "run"  \\atlas\share  i get and error that says "A duplicate name exists on the network"  

I can ping both Atlas and Titan fine.  they resolve to the same IP.    i can map to teh new shares via IP just fine. \\\share  .....

any thoughts??

Question by:razor192
LVL 44

Expert Comment

ID: 16723412
You cannot have diplicate names on a windows network.  Name the computer one name or the other, and dont have 2 names for the one computer.  It will give you trouble down the road.  Also, stop any servers that think the old system is running, reboot them.  Windows name service file sharing remembers what it should forget, and forgets what it should remember.  It is a difficult ADHD child, and needs to be treated that way.  Do NOT confuse this OS, it will bite you in the butt if you do.  One name per computer, NO duplicate names.

Author Comment

ID: 16723425
so am i understanding you correctly..    you say it is not a good idea to have a server  refered to by 2 different DNS names??    ie  and A record for Atlas that points to and an A record for Titan that also points to ??  

LVL 19

Expert Comment

ID: 16723850
The above post is incorrect. There is absolutely no reason why an IP shouldn't be resolved by 2 dns names, although I'd use a CNAME instead of 2 A records. The computer name is quite different and should obviously be individual, and as you are not running a domain it may or may not have the same name as the DNS record, it doesn't really matter from a functionality point of view.  If the old server was switched off it's probably just cached information somewhere. If you run an ipconfig /flushdns or reboot you'll probably find it's gone.
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LVL 88

Expert Comment

ID: 16724004
There might also be some remnants in the wins database, so also remove the old entries from there. hosts files on every PC can also have some old entries.
LVL 12

Accepted Solution

GinEric earned 2000 total points
ID: 16724100
You can attempt to override that error here: http://support.microsoft.com/default.aspx?scid=kb;en-us;281308

and it "is" an error; it's a basic flaw in Microsoft's approach to DNS, there is no doubt about that.

Our own DNS records clearly show more than one hostname for a specific IP Address; in fact, what Windows does not seem capable of, that is a defined feature of DNS, is that it cannot simply define a domain!

This is how Microsoft should have been doing it:

Define the domain "without" any particular hostname
Add hosts if so desired to allow for any host or server to run both multiple IP Addresses and mutliple hostnames

Windows Server, in most instances of wizards, will ask for a Domain Name when it means a hostname, and, it gets the two defintions entirely confused!

This inevitably leads to "duplicate name found on network" and Windows will then start doing the thinking for you and disrupt your organizational structure.  It is this "thinking for you" approach and the misappropriations of DNS specifications that leads to "duplicate name found on the network," which is a misnomer.

Another "goofy" report from Windows Server is the one about duplicate gateways being for redundancy; no, it is not!  Without more than one gateway per router, the Internet itself could not function!  You need at least two gateways per connection just to make a valid Internet connection.  The Internet is, after all, a set of all gateways [routers] on a network that is a set of interconnected networks, hence the name "Internet."

I'm sorry, but there are a great number of amateurs writing code and specifications at Microsoft who do not know the basic definitions.  If you want to get messages from point A to point C, and the only gateway is point B, then you have a ring network or a star network, not an Internet zone.  Internet zones require at least two paths to any other machine on a network.  The ISP's have added confusion by agreeing with the one-eyed one gateway networking approach.  That's because they assign each subscriber a single IP Address, dynamically or statically, to make the initial connection.  A lot of us out here have numerous blocks of IP Addresses and this requires more than one gateway to interconnect them all.  The same logic applies for interconnections between public gateways and private LAN gateways and/or networks.

Example:  A single server machine might be both the Primary Domain Controller [PDC] and a Mail Server and a Web Server.  In such case, the machine should have three separate names that resolve to the same IP Address.  Otherwise, DNS would be confused as to where to find "www." and "smtp." and any other host on the Internet.  These prefixes are just that, hostnames.  There is no need for such basic IP Address resolutions to have unique names, since it is the IP Address that the entirety of DNS is based upon and never the hostname!

Somehow, someone in Redmund got really confused about how DNS actually works.  DNS is based on numbers, not names.  DNS resolves IP Addresses to hosts, and not hostnames to IP Address [that is a simple Reverse Record].

Recursion:  if I have more than one hostname per IP Address, then I can also prioritize and/or resolve hostnames basically per function of the hostname.  By adding a Reverse Record, an A Record, and a Pointer, any host, regardless of the number of names it goes by, can be resolved properly.  This happens everyday on the real Internet.  As an exact and working example, Musics.com does not even need a hostname!  That is the primary record, Musics.com, and not Bach.Musics.com nor www.Musics.com nor ftp.Musics.com nor smtp.Musics.com, all different names for the exact same machine.

Some are added as CNAME's, but some are not.  The smtp record is its own standing record, so are the Name Server [NS] records.  It does not matter that the machine has more than one hostname, in fact, initially for the domain it should not have any hostname!  This makes all queries for Musics.com resolve to whatever host happens to be answering at the instant.  Say if I shut down Bach, then the next machine available as a valid Musics.com machine [Server] will answer that query, regardless of hostname.  That is how it is supposed to work.

And that is all from a real domain and real DNS records that have stood for a very long time, from the beginning of the World Wide Web.  The World Wide Web and the Internet are not to be confused; the first is a program written by Tim Berners-Lee and the second is the defined network specification used to access the World Wide Web.  All other services and protocols, ftp, smtp, etc., are second level services of the Internet.

Microsoft needs to trashcan that idea "one name per computer," it is invalid.  The rule is "one username per user" for connections, or at least that is what it is supposed to be, since a user should not be connecting from two locations simultaneously, unless there is a very specific reason and provision for doing so, but the rule for machines is "one machine per IP Address," not one hostname.  You can't have two hosts using the same IP Address; that is the real rule, there is absolutely no reason why any machine can't have more than one hostname.  In fact, even Microsoft's own mainframe network assigns multiple hostnames to the same machines.

razor192, your second statement shows where an error will occur only because both names have the same IP Address; that breaks the basic rule of one IP Address per hostname.  You fix this by assigning a different IP Address to each hostname, so that if Atlas is, then Titan, if not a CNAME, should have a different IP Address such as  if these are two separate physical machines.  Those are A Records and PTR's which will create an associated Reverse Record and it is the Reverse Record upon which all of DNS is built, not the A records and PTR's.  I can make an IP Address answer to any name by simple stating the record as *.domain.name.

And that is a Domain Name, a Fully Qualified Domain Name [FQDN], not hostname.domain.name.

hostname.domain.name. is an hostname, not a Fully Qualified Domain Name.  And this is where Microsoft drops the ball.  In Windows Server setups, Microsoft programmers refer to the FQDN using and requiring a hostname and this approach is flat out wrong.  You don't have to confuse the Windows Operating System, it is already quite confused enough by false defintions, imposed definitions, and definitions that break the Internet Standards, such as DNS.


Were it that simple!  No, Microsoft insists on keeping a hostname until the day it dies.  If you install the server software with one hostname, and later decide to change it, Active Directory will give you nightmares in trying to change a simple hostname!  If you put two NIC's in a Windows Server, it will "newthink" your desires and say "duplicate name found on network," which is totally wrong!  You wil then have to uninstall every Windows Server component, one at a time, including Active Directory and the domain controller itself, just to try to change the hostname.  And this usually doesn't work either.  Which means, in Windows, your domain is myopic with a fixed loci about the aboriginal hostname of the installed server.  Ridiculous!  From anyone's point of view.  If I want to change the hostname, change the hostname, you stupid Operating System!  I know what I'm doing, I don't need a Big Brother to do the thinking for me, and, I'm not that lazy or uneducated.  Basically, it's an insult from the authors of the server software, not a good approach to pleasing customers who pay thousands of dollars for this software to work.

Has it ever occurred to these programmers that I, and others, might actually know more than they do about this stuff?  Well, it's true, some of us "do know more" than Microsoft's employees.  And it gets really hard having to teach them when others continue to deny this and continue to support their myopic view of computers and networking.  It tends to convince Microsoft employees that they, somehow, had something to do with writing the specifications in complete contradiction to the fact that others wrote them, not Microsoft.

In the end, all we want is for our networks to work properly and our way, not Joe Schmoe's way who arrived twenty or thirty years later on the scene and now thinks he knows all about it and, like Al Gore, claims to have invented it.  Not so.  So alextoft is exactly right, there is absolutely no reason why you can't have an IP Address resovle to two names; Microsoft is wrong on this one.

As a partner, gold, certified, diamond, whatever, we intend to teach Microsoft a little more about this problem because we can't have it standing in the way of our Network Operations; it's that simple, our way or the highway.

And they do listen, everyday, on the telephone, from Redmond, Washington State.  Perhaps we'll get a rewrite by the next Service Pack.

Meanwhile, new view should work, however, some features fail by default, such as net view \\Musics.com which should not get an access denied from the Local Server console under the Administrator account.  I should not have to supply an hostname to get a view of the entirety of Musics.com network.

I don't have such problems from Linux, whose authors actually wrote the little ditty that is the net shell commandline program.

Microsoft still has a little ways to go to get to conformity itself, as it is the one "not conforming" to Internet standards.

My last question to Microsoft's Teams was "Why must you guys insist on breaking the rules?"

It's a good question, and someone is working on it somewhere at Microsoft right now.  Some rules should just be adhered to, especially on the Internet, and DNS is one of them.

For the poster: change one of the IP Addresses, for either Atlas or Titan and your shares should work.  Remember, DNS works by resolving names from IP Addresses, not the other way around.  Yet Microsoft has that function backwards as well: the IP Addresses should collide, not the names.
LVL 20

Expert Comment

ID: 16724191
"...turned the old 2k server off"
Now THAT'S the problem.
Solution would be as simple as turning "old 2k" server back ON , UNSHARE  folders on Atlas and  THEN power off the server.
"...There are some apps in the office that point to \\atlas\share  for data   so I wanted to keep the "atlas" name around ..."
Now substitute computer name "Atlas" with the correct name "Titan" and restart your network.
Next time your network is up and running browser master will ( hopefully) broadcats all available resources on network correctly ( old and nonexisting entries will be disregard and new shared folders ( on Titan) should appear in the list of shared resources on your network) .

good luck
LVL 12

Expert Comment

ID: 16725257
You still cannot have two machines with the same IP Address, but you can have one machine with many IP Addresses.

And names should not matter because resolution should be by IP Address, not by name.  Now, if you have two differenet machines with the same name on the same domain, yes, it will break, but that is not a "collision" that is a divergence, the opposite of a "collision."  The routing would fork in trying to find the correct path, unless and except it knew the IP Address first, in which case, the name can be disregarded.  But this is not usually the case.  As with most internet traffic, access is requrested first via name, so that this suggests that names must be unique.  But that is between two or more machines.  It does get kind of tricky because even with unique IP Addreses some programs, like browsers, are name dependent and do not pre-empt names for numbers.  The result is that you get two reverse records for the same name, you diverge, and you don't know which one to select, which one is the "real" name you were looking for.

It's still easier to give Titan another IP Address with the associated Atlas name and there should be no collision nor divergence.  It works just like a CNAME and Windows under each adapter has a provision for multiple IP Addresses, the hard part is in associating a name with that IP Address, since Windows makes little or no provision for it with all of its numerous "wizards."

The wizards, apparently, are not so witty as to be considered true witans.

Author Comment

ID: 16725335

http://support.microsoft.com/default.aspx?scid=kb;en-us;281308    worked like a charm..

I had initally tried to use a CNAME to get Atlas to resolve to titan.blah.com  but i could not map drives via the cnae refrence.  then I tried the 2 A records ..   and ran into the duplicate name error.  

thanks all.  prob fixed.    


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