When you enter command into Cisco iOS it immediately becomes active in running configuration. But if you reboot your router, and haven’t saved your configuration, it’s deleted.
Here are few commands that will allow you to manipulate your configurations.
Zeljko#copy running-config startup-config – Saves the running configuration to NVRAM
Zeljko#show running-config – Shows the running configuration in the terminal window
Zeljko#show startup-config – Shows the start-up configuration (in NVRAM) in the terminal window
Zeljko#erase startup-config – Erases the configuration stored in NVRAM
So if you entered few commands and want them saved to your configuration you will run copy running-config startup-config
You can reboot your router with reload command
Proceed with reload? [confirm]System configuration has been modified.
Save? [yes/no]: n