Which command enable ospf authentication?
A.
ip ospf authentication message-digest
B.
network 192.168.10.0 0.0.0.255 area 0
C.
area 20 authentication message-digest
D.
ip ospf message-digest-key 1 md5 CCNA
Explanation:
This question might be incomplete. Both ip ospf authentication message-digest and area 20
authentication message-digest command enable OSPF authentication through MD5.
Use the ip ospf authentication-key interface command to specify this password. If you enable
MD5 authentication with the message-digest keyword, you must configure a password with
the ip ospf message- digest-key interface command.
interface GigabitEthernet0/1
ip address 192.168.10.1 255.255.255.0
ip ospf authentication message-digestip ospf message-digest-key 1 md5 CCNA
Cisco Official Certification Guide, Implement Routing Update Authentication on OSPF, p.348
To enable authentication for an OSPF area, use the area authentication command in router
configuration mode.
To remove an authentication specification of an area or a specified area from the
configuration, use the no form of this command.
area area-id authentication [message-digest]
no area area-id authentication [message-digest]
http://www.cisco.com/c/en/us/td/docs/ios/12_2/iproute/command/reference/fiprrp_r/1rfospf.ht
ml
https://supportforums.cisco.com/document/22961/ospf-authentication