OSPF has five types of packets, which have the same header format. If the Auth Type field in the packet header is 1, which of the following authentication modes is used?

Question

Options

• ANon-authentication
• BMD5 authentication
• CSimple text authentication
• DHash authentication

• A
  4% (2)
• B
  2% (1)
• C
  83% (40)
• D
  10% (5)

Explanation

OSPF's Auth Type field uses a numeric code to specify the authentication method: 0 = no authentication, 1 = simple plaintext (clear-text) password, and 2 = MD5 cryptographic authentication. Auth Type 1 means the password is transmitted as plain text in the packet header, making it "simple text authentication" - option C.

Why the distractors are wrong:

• A (Non-authentication) corresponds to Auth Type 0, not 1.
• B (MD5 authentication) corresponds to Auth Type 2, the stronger cryptographic option.
• D (Hash authentication) is not a defined OSPF Auth Type value; it's a distractor conflating MD5 with a generic "hash" label.

Memory tip: Think of it as a security ladder - 0 means no lock, 1 means a simple key (plain text, easy to see), 2 means a combination lock (MD5, cryptographically secure). The higher the number, the stronger the protection.

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