The “router” command in global configuration mode is an important command for start configuration of any dynamic routing protocol. The topology displayed in Figure 1 is used to configure and demonstrate the EIGRP routing protocol. Figure 2 (marked with a red triangle) illustrates the “router ?” with question marks to demonstrate the list of dynamic routing protocol supported by the current IOS.
|To configure the routing protocol EIGRP, enter the command as shown below in the global configuration mode.
Router(config)# router eigrp <autonomous-system>
The autonomous-system argument is a 16-bit value between the number 1 and 65,535 as shown in figure 2 marked with a yellow triangle. All routers within the EIGRP routing domain must use the same autonomous system number. The configuration of the autonomous system and enable EIGRP routing protocol for the topology shown in figure 1 is the following:
Notice that the prompt has been changed from a global configuration mode prompt to router configuration mode. We have configured the autonomous system number same on all router because it is must be same on all routers to establish neighbour adjacencies. EIGRP can support multiple instances of the routing protocol, though multiple routing protocol implementation is not usually needed or recommended.
The router eigrp <autonomous-system> command is not enough for starting the EIGRP process. The command only enables the EIGRP and provides access to configure the EIGRP settings.
We can remove the EIGRP routing process from a device, using the “no router eigrp <autonomous-system>” command in global configuration mode. The command will stop the EIGRP process and removes all existing EIGRP router configurations.