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What is UDP port 389 used for? RRS feed

  • Question

  • What is UDP port 389 used for?

    Answer = LDAP queries. But what I am trying to find out is what happens if this port\protocol combo is blocked on a firewall for example on the PDCE. What happens? what are the implications?

    If I run c:>\temp>"portqry /n TargetServer /p TCP /e 389"

    I get a stack of responses.   If however I run  "portqry /n TargetServer /p UDP /e 389"

    "I get UDP port 389 is listening"

    How's this for a guess? With DNS we enable port 53 on tcp and udp. I believe UDP is enabled and used if the DNS payload breaches that. that TCP can hold. So is the same thing going on here with LDAP UDP port 389 in that the payload is too much for TCP and so UDP get's used? I have searched Microsoft and can't see a reference to what it actually does or the implication of turning it off.

    This is related to a problem I am looking at and not just a nice to know type thing.

    Thank you for looking.

    Wednesday, September 28, 2016 3:36 PM

Answers

  • Hi

     UDP Port 389 for LDAP to handle normal queries from client computers to the domain controllers.And I'd recommend you that check this article for details;

    http://blogs.msmvps.com/acefekay/2011/11/01/active-directory-firewall-ports-let-s-try-to-make-this-simple/


    This posting is provided AS IS with no warranties or guarantees,and confers no rights. Best regards Burak Uğur



    This posting is provided AS IS with no warranties or guarantees,and confers no rights. Best regards Burak Uğur

    • Marked as answer by Palmer_001 Monday, October 10, 2016 6:50 AM
    Tuesday, October 4, 2016 2:33 PM
  • These may help;

    http://www.auditmypc.com/udp-port-389.asp

    https://msdn.microsoft.com/en-us/library/cc717362.aspx

    And a similar case about UDP 389 ;

    https://social.technet.microsoft.com/Forums/windows/en-US/a6d07279-6852-4dfb-afc7-f06f5b1034c2/port-389udp?forum=winserverDS


    This posting is provided AS IS with no warranties or guarantees,and confers no rights. Best regards Burak Uğur

    • Proposed as answer by AlvwanModerator Monday, October 10, 2016 3:20 AM
    • Marked as answer by Palmer_001 Monday, October 10, 2016 6:51 AM
    Tuesday, October 4, 2016 6:16 PM

All replies

  • Hi

     UDP Port 389 for LDAP to handle normal queries from client computers to the domain controllers.And I'd recommend you that check this article for details;

    http://blogs.msmvps.com/acefekay/2011/11/01/active-directory-firewall-ports-let-s-try-to-make-this-simple/


    This posting is provided AS IS with no warranties or guarantees,and confers no rights. Best regards Burak Uğur

    • Proposed as answer by Todd Heron Wednesday, September 28, 2016 3:59 PM
    • Unproposed as answer by Palmer_001 Monday, October 10, 2016 6:50 AM
    Wednesday, September 28, 2016 3:42 PM
  • This one might also help.

    https://technet.microsoft.com/en-us/library/dd772723%28v=ws.10%29.aspx?f=255&MSPPError=-2147217396

     

     



    Regards, Dave Patrick ....
    Microsoft Certified Professional
    Microsoft MVP [Windows Server] Datacenter Management

    Disclaimer: This posting is provided "AS IS" with no warranties or guarantees, and confers no rights.

    • Proposed as answer by Todd Heron Wednesday, September 28, 2016 4:00 PM
    Wednesday, September 28, 2016 3:45 PM
  • This topic actually came up on this forum - pls refer to https://social.technet.microsoft.com/Forums/windowsserver/en-US/a6d07279-6852-4dfb-afc7-f06f5b1034c2/port-389udp?forum=winserverDS

    In short, UDP is used by the LDAP ping

    hth
    Marcin

    Wednesday, September 28, 2016 4:30 PM
  • Hi,

    Just checking in to see if the information provided was helpful. Please let us know if you would like further assistance.

    Best Regards,

    Alvin Wang


    Please remember to mark the replies as answers if they help and unmark them if they provide no help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Tuesday, October 4, 2016 1:08 AM
    Moderator
  • Hi. sorry for not getting back sooner. I'm going to read through the articles now and come back.
    Tuesday, October 4, 2016 7:43 AM
  • So this one says (see below) but does not differentiate.

    "

    TCP and UDP 389

    Directory, Replication, User and Computer Authentication, Group Policy, Trusts

    LDAP",

    Tuesday, October 4, 2016 7:46 AM
  • Hi Marcin, I came across that article before asking the question here. As you can see from reading, It appears there is not answer to what the person is asking and that is, how or what is UDP used for over port 389 as opposed to tcp over 389.
    Tuesday, October 4, 2016 7:48 AM
  • Hi

     UDP Port 389 for LDAP to handle normal queries from client computers to the domain controllers.And I'd recommend you that check this article for details;

    http://blogs.msmvps.com/acefekay/2011/11/01/active-directory-firewall-ports-let-s-try-to-make-this-simple/


    This posting is provided AS IS with no warranties or guarantees,and confers no rights. Best regards Burak Uğur



    This posting is provided AS IS with no warranties or guarantees,and confers no rights. Best regards Burak Uğur

    • Marked as answer by Palmer_001 Monday, October 10, 2016 6:50 AM
    Tuesday, October 4, 2016 2:33 PM
  • Great stuff in that link. Twice it states "

    TCP and UDP 389

    So you see. I am trying to see what specifically uses UDP, what function? All I keep seeing is 389 over udp and tcp for LDAP

    Thank you for taking the time to respond however it is appreciated.

    Tuesday, October 4, 2016 5:49 PM
  • These may help;

    http://www.auditmypc.com/udp-port-389.asp

    https://msdn.microsoft.com/en-us/library/cc717362.aspx

    And a similar case about UDP 389 ;

    https://social.technet.microsoft.com/Forums/windows/en-US/a6d07279-6852-4dfb-afc7-f06f5b1034c2/port-389udp?forum=winserverDS


    This posting is provided AS IS with no warranties or guarantees,and confers no rights. Best regards Burak Uğur

    • Proposed as answer by AlvwanModerator Monday, October 10, 2016 3:20 AM
    • Marked as answer by Palmer_001 Monday, October 10, 2016 6:51 AM
    Tuesday, October 4, 2016 6:16 PM
  • Hi,

    Just checking in to see if the information provided was helpful. Please let us know if you would like further assistance.

    Best Regards,

    Alvin Wang


    Please remember to mark the replies as answers if they help and unmark them if they provide no help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Monday, October 10, 2016 3:20 AM
    Moderator