Which two authentication types does OSPF support? (Choose two.)
A.
Plain text
B.
MD5
C.
HMAC
D.
AES 256
E.
SHA-1
F.
DES
Explanation:
BD
These are the three different types of authentication supported by OSPF
+ Null Authentication—This is also called Type 0 and it means no authentication information is included in the
packet header. It is the default.
+ Plain Text Authentication—This is also called Type 1 and it uses simple clear-text passwords.
+ MD5 Authentication—This is also called Type 2 and it uses MD5 cryptographic passwords.
Source: http://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/13697-25.html