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Intermittent Sigma communications with Microsoft's Vista, Windows 7 and Server 2008


The default dynamic port range for TCP/IP has been changed with Windows Vista and later Microsoft operating systems.

Product Line

Field Devices, Satchwell Sigma


  • Microsoft Windows Vista
  • Microsoft Windows 7
  • Microsoft Winsow 8/8.1
  • Microsoft Windows Server 2008
  • Ethernet communications
  • Microsoft Windows 10 and server 2012, when Sigma is part of an SBO/EBO front end system.


To comply with Internet Assigned Numbers Authority (IANA) recommendations, Microsoft has increased the dynamic client port range for outgoing connections in Windows Vista, Windows 7 and in Windows Server 2008. The new default port range starting at port 49152 through to port 65535. This is a change from the earlier Windows configuration that used a default port range of 1025 through to 5000.

Sigma used port 49152 as default for communications between Sigma server and Sigma controllers.


You can use SE Legacy Port Reservation to reserve the port used by Sigma.

Another resolution would be to redefine the dynamic port range Windows Server 2008 can use to 50000 to 65535, hence keeping the port free for Sigma. (Sigma port requirements can be found in What port numbers are used by the Sigma system?).

You can view the dynamic port range on a computer that is running Windows Vista, Windows 7, Windows Server 2008 or 2012 by using the following netsh commands:

netsh int ipv4 show dynamicport tcp
netsh int ipv4 show dynamicport udp
netsh int ipv6 show dynamicport tcp
netsh int ipv6 show dynamicport udp

Note The range is set separately for each transport and for each version of IP. The port range is now truly a range with a starting point and with an endpoint. Microsoft customers who deploy servers that are running Windows Server 2008 or 2012 may have problems with RPC communication between servers if firewalls are used on the internal network. In these cases, we recommend that you reconfigure the firewalls to allow for traffic between servers in the dynamic port range of 49152 through 65535. This range is in addition to well-known ports that are used by services and by applications. Or, the port range that is used by the servers can be modified on each server. You adjust this range by using the netsh command, as follows:

netsh int set dynamic start=number num=range

This command sets the dynamic port range for TCP. The start port is number, and the total number of ports is range. The following are sample commands:

netsh int ipv4 set dynamicport tcp start=10000 num=1000
netsh int ipv4 set dynamicport udp start=10000 num=1000
netsh int ipv6 set dynamicport tcp start=10000 num=1000
netsh int ipv6 set dynamicport udp start=10000 num=1000

These sample commands set the dynamic port range to start at port 10000 and to end at port 10999 (1000 ports). The minimum range of ports that can be set is 255. The minimum starting port that can be set is 1025. The maximum end port (based on the range being configured) cannot exceed 65535. To duplicate the default behavior of Windows Server 2003, use 1025 as the start port, and then use 3976 as the range for both TCP and UDP. This results in a start port of 1025 and an end port of 5000.

Note When you install Microsoft Exchange Server 2007 on a Windows Server 2008-based computer, the default port range is 1025 through 60000.

Click here to be linked to the Microsoft Knowledge Base Article Number 929851.

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