|  | 12.1 | Initial Router Configuration
| 12.1.7 | Using the ip default-network command

In the example, the global command ip default-network 192.168.17.0 defines the Class C network 192.168.17.0 as the destination path for packets that have no routing table entries. Router A could need a firewall for routing updates. The Company X administrator does not want updates coming in from the public network. Router A may need a mechanism to group those networks that will share Company X's routing strategy. One such mechanism is an autonomous system number.