Hello Hussein
Cisco commands are implemented using a specific hierarchy. When you type the command ip eigrp ?
, the resulting commands all have to do with EIGRP and its functionality. They are limited to routing EIGRP and nothing else. However, authentication is a different entity and must be placed within a different category. This is why the commands fall under the ip authentication
keywords even though the authentication is being configured for EIGRP. Anything under the ip authentication ?
will belong to the authentication functionality of the router.
So by typing ip authentication mode eigrp AS_NUM md5
you are not configuring something specific to EIGRP but something specific to the authentication functionality of the router.
I hope this has been helpful!
Laz