正解:A
To configure two Cisco Nexus 9000 switches as EIGRP neighbors, the key chain and EIGRP router configuration must be consistent and correctly referenced. Chosen configuration meets all the requirements:
* key chain eigrp: Defines the key chain used for authentication.
* key 1 key-string CISCO: Specifies the authentication key and string for the key chain.
* router eigrp NXOS: Configures EIGRP for the NXOSinstance.
* autonomous-system 12: Specifies the autonomous system number for EIGRP.
* authentication mode md5: Configures MD5 as the authentication mode.
* ip authentication key-chain eigrp NXOS EIGRP: Binds the key chain to the EIGRP
process on the interface.
* ip authentication mode eigrp NXOS md5: Enables MD5 authentication on the
interface.