Scenario: A user leaves the organization and you would like to forward their number/calls to a manager.

Solution: Microsoft has a Lync Server 2013 (and 2010) Resource Kit that contains a command-line tool called SEFAUtil (secondary extension feature activation) which can be used to achieve this task.  Before beginning, I would recommend taking a look at the official TechNet article/documentation on the utility itself: http://technet.microsoft.com/en-us/library/jj945604.aspx  In this tutorial, we will download the tool and execute the proper commands to configure call forwarding for a specified user.

1. Download a copy of the Lync Server 2013 Resource Kit from Microsoft's website here: http://go.microsoft.com/fwlink/p/?LinkID=330429
2. Run the installer from your Front End Server/Pool
   
   
   
   
   
   
3. Create a trusted application pool
   1. Execute the following command
      1. $Site=Get-CsSite -Identity "My Site"
         
         
         1. Note: If you don't know what to substitute for My Site, execute the following command to see what sites you have available and then use the Identity value.
            1. Get-CsSite
               
               
      2. Execute the following command
         1. New-CsTrustedApplicationPool -id <Pool FQDN> -Registrar <Pool Registrar FQDN> -site $Site.SiteID
            
            
            1. Note: Technically we didn't need to run the 1st command, however this can help cut-down on user error.  Additionally, if you have multiple sites and you knew what site you wanted to use but not the ID, this helps skip a step.
4. Define SEFAUtil as a trusted application in the Lync topology
   1. Execute the following command
      1. New-CsTrustedApplication -ApplicationId sefautil -TrustedApplicationPoolFqdn <Pool FQDN> -Port 7489
         
         
5. Enable the Lync topology to commit the changes
   1. Enable-CsTopology
      
      
6. Forward a user's number
   1. Navigate to %ProgramFiles%\Microsoft Lync Server 2013\ResKit
      
      
   2. Execute the following command
      1. SEFAUtil.exe /Server:<Pool FQDN> [email protected] /enablefwdimmediate /setfwddestination:[email protected]
         
         

That should be it!

Note: If you are more comfortable using a GUI or don't wish to type in multiple powershell commands, I would highly recommend checking out Johan Veldhuis's SefaUtil GUI PowerShell script.  Once you are done following steps 1-5 above, you you can grab a copy of the script here: http://johanveldhuis.nl/sefautil-gui/sefautil-gui/