Chapter 2 Advanced Routing for FortiOS 5.0 : Dynamic Routing Overview : Comparison of dynamic routing protocols : When to adopt dynamic routing
  
When to adopt dynamic routing
Static routing is more than enough to meet your networking needs when you have a small network. However, as your network grows, the question you need to answer is at what point do you adopt dynamic routing in your networking plan and start using it in your network? The main factors in this decision are typically:
Budget
Current network size and topology
Expected network growth
Available resources for ongoing maintenance