Static Routing

You add network tunnel groups to Secure Access to enable secure network connections to the internet and private resources. When setting up a network tunnel group, you can choose static routing or dynamic routing (when you have a BGP peer for your on-premise router).

Use static routing for small, simple networks where predictable routes are needed and manual configuration is manageable. You might want to use static routes in the following cases:

Your networks use an unsupported router discovery protocol.
Your network is small and you can easily manage static routes.
You do not want the traffic or CPU overhead associated with routing protocols.
In some cases, a default route is not enough. The default gateway might not be able to reach the destination network, so you must also configure more specific static routes, such as a static route to an "inside network" when you need to explicitly direct traffic to a specific internal network segment that isn't reachable through the default gateway or via dynamic routing protocols.
You are using a feature that does not support dynamic routing protocols.
Note that advertising a default route using static routing is not supported and can lead to traffic disruptions.

Routing Options and Guidelines < Static Routing > Dynamic Routing Using BGP