What is the purpose of using the ip ospf message-digest-key key md5 password command and the area area-id authentication message-digest command on a router?​

What is the purpose of using the ip ospf message-digest-key key md5 password command and the area area-id authentication message-digest command on a router?​

• to encrypt OSPF routing updates​
• to enable OSPF MD5 authentication on a per-interface basis​
• to configure OSPF MD5 authentication globally on the router​
• to facilitate the establishment of neighbor adjacencies
  

  Answers Explanation & Hints: To configure OSPF MD5 authentication globally, the ip ospf message-digest-key key md5 password interface configuration command and the area area-id authentication message-digest router configuration command are issued. To configure OSPF MD5 authentication per interface, the ip ospf message-digest-key key md5 password interface configuration command and the ip ospf authentication message-digest interface configuration command are issued. Authentication does not encrypt OSPF routing updates. The requirements to establish OSPF router neighbor adjacencies are separate from authentication.​