Part 3. How’d ya like to trade in that old PBX for a shiny new OCS environment?

On to OCS…  There isn’t much to the mediation install, so we’ll skip over that and go right to the mediation configuration.  Keep in mind; you want to have 2 separate network interfaces on your mediation server.  One will be used to route traffic to the VoIP gateway and the other 2 the data network.  THESE SHOULD NOT BE THE SAME PHYSICAL INTERFACE OR ON THE SAME SUBNET!!!  Sorry for all the yelling, but it’s important.


For my network I have utilized the following

  • Data Network: 172.16.5.x
  • Voice Network: 172.16.11.x
  • VoIP Interface IP:
  • VoIP Gateway IP:
  • Data Interface IP:

When configuring the NICs you’ll want to make sure you only give the data network interface a default gateway, we want to reserve the VoIP NIC for VoIP only so we don’t want a default gateway there.

After the install we have a few things to configure, well start at the Forest level>Voice Properties.

Create a new profile by clicking “Add” type in a name for your new profile, then we’ll need to add a normalization rule.  We’ll start by adding a 7 digit dialing rule that will add a + sign to any 7 digit number:

 7 Digit Dial

We’ll go ahead and add 1 more rule, to strip (513)xxx-xxxx  down to a standard 7 digit dial with a +.  This is useful if you need to strip the area code or something of the like.


Now we’ll create a default route to send everything to the mediation server:


Now that the forest is ready, let’s configure our mediation server.

 Open up the OCS snap-in under Administrative Tools.  Expand your Forest, expand Mediation Servers, right click your mediation server and go to “properties”.

Here we configure our Communications Server listening IP Address (the IP for the data network) and the Gateway listening IP (VoIP Network IP).  In this example I am using TCP for my gateway, TLS is an option too depending on your device.


For “Office Communications Server next hop” use your standard edition pool.  For the PSTN gateway we will use the IP of our VoIP Gateway. 


 On the certificates tab select a certificate the matches the FQDN of your mediation server.



Now all we have to do is EV enable a user and set their Line URI.  Right click the user, go to “Properties”, choose “Configure” next to telephony settings:


Configure your user as below (substitute extensions for your environment) and you’re all set.


Keep in mind, you’ll need to manipulate numbers at the gateway for DID (Direct Inbound Dial).

So that’s it for “Shiny New OCS”, please feel free to comment if you have questions or want more detail.

About Kevin Peters

My name is Kevin Peters.
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