|  | 12.1 | Initial Router Configuration
| 12.1.3 | How a router learns about destinations

By default, routers learn paths to destinations three different ways : static routes -- manually defined by the system administrator as the next hop to a destination; useful for security and traffic reduction default routes -- manually defined by the system administrator as the path to take when there is no known route to the destination dynamic routing -- the router learns of paths to destinations by receiving periodic updates from other routers.