As I’m sure you know, a switch switches and a router routes. Among other things, It routes packets of data and it routes requests. Listed below are five ways that a router will automatically initiate a routing request.
1. The router has been booted or rebooted.
2. A primary IP address was changed. An interface has several secondary IP addresses but only one primary IP address. If that IP address has been changed, the router will start a routing request out its interface.
3. Of course, if the interface goes down this will automatically cause a routing request.
4. If you make a change to the router’s configuration such as an IP address change.
5. If you issue the clear ip route command.