Option A is the correct configuration to apply interface and sensor monitoring on a router with the given requirements. This option uses SNMPv3, which is the most secure version of SNMP that supports encryption and authentication. The configuration steps are as follows12:
* Create an access list named nms that permits only the NMS server with IP address 10.15.2.19 to access the router: ip access-list standard nms and permit 10.15.2.19 0.0.0.0.
* Create a view named rw that includes all the SNMP objects: snmp-server view rw included.
* Create a group named nms that uses SNMPv3 with privacy (encryption) and authentication, and assigns the view rw and the access list nms to the group: snmp-server group nms v3 priv read rw access nms.
* Create a user named nms that belongs to the group nms and uses DES for authentication and AES for encryption, with the passwords despass and aespass respectively: snmp-server user nms nms v3 auth des despass priv aes 192 aespass.
Option B is incorrect because it does not use encryption for SNMP communication, which is required by the question. The noauth keyword in the snmp-server group command means that no authentication or encryption is used, which makes the SNMP packets vulnerable to eavesdropping and tampering1.
Option C is incorrect because it does not use the most secure algorithms for SNMP communication, which is required by the question. The md5 and des keywords in the snmp-server user command mean that MD5 and DES are used for authentication and encryption respectively, which are considered weak and outdated algorithms. AES and SHA are recommended instead1.
Option D is incorrect because it does not restrict the access to the NMS server only, which is required by the question. The snmp-server community command creates a community string that acts as a password for SNMP access, but it does not specify an access list to limit the source IP addresses that can use the community string. Therefore, any device that knows the community string can access the router via SNMP1. References: 1: Configuring SNMPv3, 2: SNMP Configuration Guide, Cisco IOS XE Gibraltar
16.12.x