|  | 12.1 | Initial Router Configuration
| 12.1.2 | Initial IP routing table
Initially, a router must refer to entries about networks or subnets that are directly connected to it. Each interface must be configured with an IP address and a mask. The Cisco IOS software learns about this IP address and mask information from a configuration that has been input from some source. The initial source of addressing is a user who types it into a configuration file. In the lab that follows, you will start up your router in a just-received condition, a state that lacks another source for startup configuration. This condition on the router will permit you to use the setup-mode command facility and answer prompts for basic configuration information. The answers you enter will include address-to-port commands to set up router interfaces for IP.