What is also called Type 0 authentication in OSPF on Cisco Routers?

A.
MD5

B.
There is no Type 0 authentication

C.
SHA1

D.
Null

Explanation:
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.
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