File access issue using NAT Router on Windows Server 2003


  • Hi,

    Setup: [Company Network <--> Windows Server 2003 acting as a NAT router <--> Private Network] We have a Windows Server machine setup as a NAT router to allow access to company file servers from  the computers on a local (private) network in a lab setup within the same building of the company. Because of the nature of the experiment/R&D setup, there is a need to have a local (private) network that can not directly access/connected to the rest of the company network.

    Issue: If we have 2 computers on the private network running 140 processes each and each process is trying to access a different file on the same file server within the company, we get many "TCP/IP has reached the security limit imposed on the number of concurrent TCP connect attempts" warnings in the event log and process terminates with "file could not be accessed" error, but if we run 280 processes from 1 computer on the private network to access 280 different files on the same company file server, everything seems to run ok.

    Help needed: Has anyone seen a similar issue before? Is there any suggestion on finding if there exists any limitation or setting in NAT router configuration that may avoid/solve the issue?

    Additional Information: If we try to use 2 PC connected to company network for running 140 processes each and each process trying to access a different file on the same file server within the company, that also seems to be running ok. This hints that there is some limitation/problem the way NAT router may be configured.



    Wednesday, February 29, 2012 4:12 AM



    Hi Niresh,

    Thanks for posting here.

    According to the testing you performed in this environment I think this is expected phenomenon and I believe this is some sort of self-protection mechanism at server level but no RRAS in order to make the server can healthy running and providing service in best situation.

    Event ID 4226 — TCP/IP Network Performance

    Some tips in the third party link below may will help us to adjust the settings :

    Meanwhile, tips in the performance tuning guide for Windows server 2003 will also help us to optimize networking performance for this server in best practice :

    Important Note: This response contains a reference to a third party World Wide Web site. Microsoft is providing this information as a convenience to you. Microsoft does not control these sites and has not tested any software or information found on these sites; therefore, Microsoft cannot make any representations regarding the quality, safety, or suitability of any software or information found there. There are inherent dangers in the use of any software found on the Internet, and Microsoft cautions you to make sure that you completely understand the risk before retrieving any software from the Internet.


    Tiger Li

    Tiger Li

    TechNet Community Support

    Thursday, March 01, 2012 9:23 AM