The OSPF protocol has authentication capabilities for all data packets exchanged between neighboring routers. In an OSPF system, which of the following algorithms does OSPF support?

Question

Options

• ADES
• BAES
• CMD5
• DSHA

• A
  14% (3)
• B
  5% (1)
• C
  77% (17)
• D
  5% (1)

Explanation

OSPF version 2 (OSPFv2) defines three authentication types in RFC 2328: Type 0 (no authentication), Type 1 (plaintext password), and Type 2 (MD5 cryptographic authentication), making MD5 the only cryptographic algorithm natively supported for authenticating OSPF packets between neighbors. DES is a symmetric block cipher used for encryption, not message authentication, and OSPF has no defined authentication type for it. AES is also a symmetric encryption cipher rather than a hashing algorithm, and while OSPFv3 can leverage AES indirectly through IPsec, it is not a built-in OSPF authentication algorithm. SHA, though a valid hashing algorithm, is not part of the OSPF authentication type definitions in the core RFC and is therefore not a supported option in standard OSPFv2 authentication.

Memory tip: Think "OSPF authenticates with MD5" -- both are foundational networking standards from the early 1990s that became the default choice in their respective domains.

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