Windows 2003 Server USN Differ

Posted on 2006-06-01
Last Modified: 2008-01-09
I have two domain controllers in my domain.  On the first dc I promoted, the Current: and Original: Update Sequence Numbers (USNs) are 4411.  This dc holds all roles.  The second dc has the Current: and Orginal: Update Sequence Numbers (USNs) of 8258.  I found this by going to ADUC, went to the View tab and selected Advanced Features, selected System, then DomainUpdate, the right-clicked Windows2003Update and selected properties.  My question is, should the USN numbers match on both controllers?  Should both dc1 and dc2 either have 4411 or 8258?  Or can these be different.  I am asking this because I am trying to install exchange 2003 standard and I thought I read where these numbers should match.  Other than that, I am not getting any event viewer errors in either Directory Service or File Replication Service and the system seems to be working well.  No other problems or quirks have been reported.  FYI, I am not installing exchange on a dc, I have another computer that I will install it on.  
Question by:rpsne
    LVL 48

    Assisted Solution

    Hi rpsne,

    mine dont match and exchange runs perfect - where did you read this?
    LVL 4

    Expert Comment

    LVL 8

    Accepted Solution

    Each object in AD has a USN number, kinda like a counter. Whenever you update a object, it increments the counter so other DC can recognize which is the new value for that object and update it accordingly. The whole AD itself has like a USN number. Same purpose.

    Your USN numbers will NEVER match between any domain controllers because as things change in network, USN number keeps changing and replication tries to catch up with it. Even if a user tries a wrong password, usn number is changed coz now the field "unsuccesful password attempts" is increased and other domain controller has to know about it to track the exact number of incorrect password attempts.

    The way you have to check of replication USN is like this..
     Install support tools.
    Open command prompt, type
    repadmin <dcname> /showutdvec dc=domainname,dc=com

    This will output the USN number of different DC's. Now do the same from another DC.

    What you have to compare is the version difference between DC's. In the first command, look for USn number of server you used. Compare this number with USN of same server when you run this command in another server.

    Try this and see how close this is. This tells you if there are replication issues...

    Also exchange doesnt care if USN are different in DC's. BUt make sure you run adprep and domain prep on schema master and domain naming master reapectively.. It is very important...



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