Configuring Forefront Threat Management Gateway for OCS 2007 R2 Part 1

The reverse proxy installation can be confusing if you have never done it before. In this scenario I will be standing up a new server to replace my ISA 2006 SP1 Server. I will create all of the rules from scratch and walk through the installation.

Network Configurations

The most important part of this reverse proxy setup is the networking configuration. It is recommended to have at least two network interfaces on the TMG server, in my case we have a network card in the DMZ with public IP addresses and one on the internal network. Depending on your actual network configuration this could be different.

An important thing to note is that in windows you can have multiple network interfaces on different networks, but not multiple default gateways. Because of this, we need to choose an adapter with the default gateway, and one without any gateway, using manual routes to get to internal resources. In most scenarios it would be ideal to assign the default gateway to your internet facing NIC, this is because it is impossible to enter manual routes for all possible internet traffic. The internal or DMZ NIC typically has no gateway, but we will assign persistent routes for the internal networks.

In my case, the NIC is directly on the internal network, so servers can communicate directly on the same subnet with no routing needed. However, I will show you how to configure these routes for another internal network to simulate the need to route. In an edge server configuration you will need routes for the desktops as well as servers, so it is important to know how to do it.

In my situation, the address spaces involved will be as follows:

Server LAN:

Desktop LAN:

DMZ: Public IP addresses

Because my TMG server has a NIC directly on the network I do not need a route for that network, but in order to talk to the network, I will need persistent routes. To see the route setup on your server:

Open a command prompt as administrator

Type Route Print and hit enter


Your output should resemble something like the picture above. Note the network has routes directly on that link, and the default gateway is set to our public interface.

To add a route to the network type the following at the command prompt and hit enter:

route add –p MASK

Where is the router on your network.

If you see OK! after you hit enter, the command took succesfully.


This means any requests for that network are in the route table, and are to go to, which will happen via the interface, or our Internal interface.

This is a fairly basic network configuration, in most environments it will be more complex and involve more subnets. However hopefully this gives you a good idea of how to setup the network in your environments.

TMG Installation

Before I get started, the diagram below will show the basic environment as it relates to the reverse proxy and my OCS Pool.


Update the server with the latest patch levels, and then launch the TMG Install. You will get a screen prompting you to Perform Updates, Run the Preparation Tool, or Run Installation Wizard.


Select Run Preparation Wizard. This Wizard will add the server role required for TMG to operate on the server. As you click through the installer you will have to choose a type of installation, choose Forefront TMG services and management for a complete install.


Let the wizard run, it will install all roles and services needed. When completed you will be presented with a screen that shows Success or Failure, Click Finish and Launch the TMG Installation Wizard.


The installation wizard will have a few defaults to accept, and then you will be asked to choose your internal network ranges. Choose Add, then choose Add Adapter. Select the Internal network interface on the server. If you previously entered persistent routes you will notice those subnets show up as being associated with that adapter as well.


Hit OK twice and your window should look something like this:


The address ranges should reflect your DMZ adapter address and any internal networks you will be routing to.

Hit Next twice to acknowledge the services that will be restarted during the install. The next page will notify you that forefront will create rules to allow domain traffic to domain controllers listed


If this information looks correct, hit Next, then Install and let the installation complete.


The installation will take some time to complete, but once it is done you should see this screen, click Finish to launch the configuration wizard.

image The initial configuration wizard will then launch. Note: You can import ISA 2006 XML configuration files to this if you do not wish to recreate your rules. I am going to start from scratch however to show the whole configuration process.


Run the wizard to configure network settings. This setup is an Edge Firewall configuration. Choose Edge and click next.


Choose your internal network adapter to be associated with the LAN. You may also enter routes here, I am not sure if this makes the previous routes entered not needed, but I will do more testing and update the blog if that changes.

imageThen choose your external adapter, in my case labeled DMZ

imageConfirm the information, and choose Finish.

imageJust to continue through the wizards, although not necessary needed, you can choose Configure System Settings which basically has you confirm the computer and domain settings.


The next step is to define Deployment Options which chooses your license information, and update settings. I will not cover that in this post.


Once you launch the TMG Console, you will notice a somewhat familiar interface with a whole lot of new features.


OCS Website Publishing Rules

Before starting with any OCS rules you should import the public certificates for your OCS Web Farm.

You should have a standard SSL certificate with a common name that matches the External Web Farm FQDN you specified during setup, or that name should reside on a UCC certificate. Either way, you must import that certificate into the Local Computer store with a valid Private Key before it can be used with ISA.

To do so, open the certificates MMC.

Right click on the Personal certificates store and choose All Tasks –> Import

imageIn the certificate import wizard, select the certificate file for your web farm certificate.

imageHit Next, enter the password used when exporting the certificate private key.

imageHit Next, choose to place the certificates in the following store, Personal should be selected.


Hit Next, then Finish. Your certificate should now be ready for use with ISA. 

For OCS, we are simply concerned with Firewall Policies, there are a lot more features to TMG 2010, which I hope to cover at a later date.

Select Firewall Policies, and choose Publish Web Sites from the tasks pane on the right

imageEnter a name for the rule such as OCS Web Components

imageHit Next, for a rule action choose Allow.

imageHit Next, choose Publish a single website or load balancer.image    Hit Next, choose Use SSL to connect to the published web server or server farm.

imageHit Next, for the internal site name enter your internal web farm FQDN, usually the pool name. If the ISA server cannot resolve that pool record, you can specify a computer or IP address as well.


Hit Next, for the path enter /* to allow all traffic to the pool for the various services.

imageHit Next, for the public name, enter your external web farm FQDN. You should have set this during install, or manually configured later.

image  Hit Next, choose New to create a new web listener. Enter a name for the listener such as OCS Web Listener.

imageHit Next, choose require SSL secured connections with clients.

imageHit Next, for the web listener IP address choose the External Network, hit Select IP Addresses.

Choose the radio for Specified IP Addresses on the forefront TMG Computer in the selected network. 

Select the IP address that will your web farm FQDN dns A record points to, and choose Add so it shows in the selected IP addresses column.

imageHit Ok, then Next. For the Listener SSL Certificates make sure Assign a Certificate for Each IP Address is selected.

Highlight the IP address and choose Select Certificate…

The next page will show you the valid certificates installed to the local computer personal store on your server. Choose the certificate for your OCS web Components and choose select.

imageHit Next, for authentication settings choose No Authentication from the drop down menu.


Hit Next twice, choose Finish to complete the listener configuration, you will be brought back to the web site publishing wizard with the new listener selected.

Hit Next, for authentication delegation choose No Delegation, but client may authenticate directly.

imageHit Next twice accepting the defaults, and choose Finish to create the rule.

Make sure you hit Apply to actually commit the rule.

imageOnce the rule is created, TMG 2010 has built in tools to test that rule for you. Right click on the rule and choose Properties. Then select Test Rule.

imageIf everything is working, including certificates, and authentication access, you will see all green. Any errors will have descriptions of the problem and how to fix it.

image   A new feature of TMG 2010 is a path ping, that basically is a traceroute of the path taken to get there. Use this to verify your routing configuration from before.


Now that this rule has been configured and you have an external DNS A record pointing to your External Web Farm FQDN, your users should be able to access the OCS web components remotely.

In the next post I will outline configuring TMG 2010 for Communicator Web Access.


About Randy Wintle

Unified Communications Architect

Posted on May 28, 2010, in Forefront TMG 2010, Networking, OCS 2007 R2, Server 2008 R2, Unified Communications. Bookmark the permalink. 6 Comments.

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