NTP traffic blocked by ASA 5510

Posted on 2009-04-22
Last Modified: 2013-12-05
When I tried to sync the time with the external NTP server with my server which has IP of, I see my server's NTP client software is polling data forever.
I checked the firewall and I see the following message.
4      Apr 22 2009      08:25:34      419002       Duplicate TCP SYN from inside: to outside: with different initial sequence number

Please help me.

Question by:atlasdev
    LVL 15

    Expert Comment

    Do you know if the external server actually uses TCP?  I think just about every implementation I've ever seen is using UDP..
    Maybe you can flip this on the client and try?

    If I try to telnet to that server's IP port 123 it just times out.. so it's at least not publically available for TCP.

    Accepted Solution

    I dont know why. But after I reboot the server. This error message is gone.....
    anyway, the problem is fixed by a simple reboot of the server....

    Featured Post

    Why You Should Analyze Threat Actor TTPs

    After years of analyzing threat actor behavior, it’s become clear that at any given time there are specific tactics, techniques, and procedures (TTPs) that are particularly prevalent. By analyzing and understanding these TTPs, you can dramatically enhance your security program.

    Join & Write a Comment

    Suggested Solutions

    My previous article  ( one possible method to get SCCM 2007 installed an…
    On a regular basis I get questions about slow RDP performance, RDP connection problems, strange errors and even BSOD, remote computers freezing or restarting after initiation of a remote session. In a lot of this cases the quick solutions made b…
    Hi everyone! This is Experts Exchange customer support.  This quick video will show you how to change your primary email address.  If you have any questions, then please Write a Comment below!
    Excel styles will make formatting consistent and let you apply and change formatting faster. In this tutorial, you'll learn how to use Excel's built-in styles, how to modify styles, and how to create your own. You'll also learn how to use your custo…

    734 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    18 Experts available now in Live!

    Get 1:1 Help Now