Chapter 2 Advanced Routing for FortiOS 5.0 : Intermediate System to Intermediate System Protocol (IS-IS) : Simple IS-IS example : Network layout and assumptions
  
Network layout and assumptions
It is assumed that each FortiGate is operating in NAT mode.
All interfaces have been previously assigned and no static routes are required.
The AFI (Authority and Format Identifier) used is 49 : Locally administered (private).
The Area identifiers are 0048 and 0049.