Using PowerShell To Restrict MSDTC Ports

Ever tried to create a linked server that uses MSDTC only to find yourself blocked by your company firewall? Ever tried to run a WMI query against a server just to find yourself blocked? Ever had the firewall team tell you that they aren’t going to open up ports 49152-65535 so that you can use RPC?

Let’s be fair, your network team shouldn’t have to open up all those ports because RPC responds somewhere within a large dynamic range.

How to configure RPC dynamic port allocation to work with firewalls will tell you how to edit your registry to restrict that port range and make your network admin a little happier.

Working with the registry is not fun at the best of times, and when you are setting up a bunch of machines it takes time. Sure, you could create a .reg file and run that on each machine, but this is 2011 and we have PowerShell now.

 

The following script checks and if necessary adds the required registry keys to restrict that port range. In the example below windows is being limited to ports 5000-5200.

 

 

<#

.SYNOPSIS

   Restricts the RPC ports to be used on Windows from 5000-5200

.DESCRIPTION

   Execute to add registry entries on the local machine to restrict the RPC ports from 5000-5200. Requires a reboot once executed.

.PARAMETER <paramName>

   NONE

.EXAMPLE

   NONE

#>

 

if (Test-Path 'HKLM:SOFTWAREMicrosoftRpcInternet' -ErrorAction SilentlyContinue) { "Registry Key Exists" } 

else { md 'HKLM:SOFTWAREMicrosoftRpcInternet' }

 

if (Get-ItemProperty -Name "Ports" -Path 'HKLM:SOFTWAREMicrosoftRpcInternet' -ErrorAction SilentlyContinue ) { "Ports value exists" }

else { New-ItemProperty 'HKLM:SOFTWAREMicrosoftRpcInternet' -Name 'Ports' -Value '5000-5200' -PropertyType 'MultiString' }

 

if (Get-ItemProperty -Name "UseInternetPorts" -Path 'HKLM:SOFTWAREMicrosoftRpcInternet' -ErrorAction SilentlyContinue ) { "UseInternetPorts value exists" }

else { New-ItemProperty 'HKLM:SOFTWAREMicrosoftRpcInternet' -Name 'UseInternetPorts' -Value 'Y' -PropertyType 'String' }

 

if (Get-ItemProperty -Name "PortsInternetAvailable" -Path 'HKLM:SOFTWAREMicrosoftRpcInternet' -ErrorAction SilentlyContinue ) { "PortsInternetAvailable value exists" }

else { New-ItemProperty 'HKLM:SOFTWAREMicrosoftRpcInternet' -Name 'PortsInternetAvailable' -Value 'Y' -PropertyType 'String' }

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