Citrix states in their article: CTX107050

Document ID: CTX107050, Created on: Jun 30, 2005, Updated: May 22, 2006

Products: Web Interface for Presentation Server 4.0, Citrix Presentation Server 4.0 for Microsoft Windows 2000, Citrix Presentation Server 4.0 for Microsoft Windows 2003, Citrix Password Manager 4.1, Citrix Presentation Server 4.0 x64 Edition, Advanced Access Control 4.0

Introduction

The Citrix Access Management Console provides a centralized management tool for the Citrix Access Suite family of products. The Access Management Console may often require access across various firewall policy zones to fully manage Citrix products such as Web Interface or the Access Gateway Enterprise. The policy zone may be between remote sites separated by a secure, policy restricted access list or from an internal, trusted management console to a Web Interface hosted in the DMZ.

The underlying system of communication for the Access Management Console is the Distributed Component Object Model (DCOM). DCOM allows an application to determine dynamically what port to use for communication from the client to server. While designed to remove the possibility of port conflicts between clients and servers, the default configuration of DCOM is to use UDP and connect to any port between 1024 and 65535. Some state-full firewalls do not keep state on UDP connections and the wide range of ports used in the default configuration of DCOM may conflict with a strong firewall policy.

DCOM communication can be restricted to TCP as well as a specified range of ports by modifying the registry on the server system hosting the DCOM based service. In the case of the Access Suite, this would be any Presentation Server, Web Interface, or Access Gateway Enterprise system managed from the Access Management Console.

Configuring Managed Servers

On a Windows 2000 server and later, the default should be to use TCP for DCOM. This should be verified on all servers that will be managed by the Access Management Console by confirming the registry key:

HKEY_LOCAL_MACHINE\Software\Microsoft\Rpc\DCOM Protocols

has the protocol value “ncacn_ip_tcp” listed first in the REG_MULTI_SZ data list.

To restrict the range of ports used in DCOM communication, the following must be performed on each server you manage with the Access Management Console:

1. Create the registry key HKEY_LOCAL_MACHINE\Software\Microsoft\Rpc\Internet

2. Create a new REG_MULTI_SZ value HKEY_LOCAL_MACHINE\Software\Microsoft\Rpc\Internet\Ports

Each line is a set of port ranges. For example:
6000-7000
7001
8000-9000

3. Create a new REG_SZ value HKEY_LOCAL_MACHINE\Software\Microsoft\Rpc\Internet\PortsInternetAvailable = “Y”

4. Create a new REG_SZ value HKEY_LOCAL_MACHINE\Software\Microsoft\Rpc\Internet\UseInternetPorts = “Y”

Note: Assigning “N” to this registry value will indicate which ports will not be used by DCOM. Assigning a “Y” to this registry value will indicate which ports will be used in DCOM communication.

Finally, the firewall policies between the Access Management Console and the managed Citrix products will require the appropriate rules for Access Management Console operation.

Source Addr
Source Port
Destination Addr
Destination Port

Access Management Console
Any
Managed Servers
TCP 135

Access Management Console
Any
Managed Servers
Configured DCOM Port Range

Much of this information is detailed in the MSDN Library article Using Distributed COM with Firewalls.

Deployment Considerations

When specifying a range of DCOM ports, a conservative value would be 1,000. For example, specifying TCP 7000 – TCP 8000. A smaller range could be specified, but failing to allow for enough DCOM ports will prevent some connections from occurring. In many cases the error may not be apparent and reported as a generic connection error.

Before specifying the range of DCOM ports on a Presentation Server, it may be necessary to profile a server’s port usage with netstat or another port monitoring utility. The range of ports specified in the registry should not conflict with existing services and should allow for a busy or heavy DCOM dependent system. For a typical Presentation Server, this should not be a large issue since most Presentation Servers run client components and not a server side component hosting a DCOM interface.

The Access Management Console should run with Citrix Administrator account privileges. The assumption in any deployment scenario is that the workstation running the Access Management Console can properly authenticate the Citrix Administrator account and will require the appropriate access policy for authentication.

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