Ipsec configuration

Hi All

I am trying ipsec configuration in a test lab. I am going through microsoft article “Setting Up IPsec Domain and Server Isolation in a Test Lab” http://technet.microsoft.com/en-us/library/cc782433(WS.10).aspx .
I want to know while configuring filter list ” domain controller”

Why they have given a Destination address of a domain controller itself. Please Clarify.
If anyone have IPsec configuration examples please forward.

Thanks