Which of the following descriptions about OSPF packet authentication is wrong? (Multiple choice)

Question

Options

• AThe authentication modes supported by Huawei routers can be divided into Null, Simple-, MD5, and HMAC-MD5 according to different encryption algorithms. Some devices also support HMAC-SHA256.
• BThe OSPF Hello packet authentication process is completed by exchanging Hello packets
• CHuawei routers support two authentication methods: area authentication and interface authentication
• DIf two OSPF devices belong to the same router, if Area 0 uses MD5 authentication, other areas must also use MD5 authentication, but the authentication keys in different areas can be different

• A
  11% (5)
• B
  70% (32)
• C
  20% (9)

Explanation

Options B and D are incorrect statements about OSPF authentication.

B is wrong because OSPF authentication is not limited to Hello packets - it applies to all OSPF packet types (Hello, DBD, LSR, LSU, and LSAck). The authentication field is embedded in the OSPF common packet header, meaning every packet exchanged between neighbors must pass authentication, not just Hello packets.

D is wrong because OSPF area authentication is configured independently per area - there is no requirement that all areas use the same authentication method. Area 0 can use MD5 while Area 1 uses Simple or Null. The only hard rule is that two routers forming a neighbor relationship on the same link/area must agree on the authentication type and key.

Why A and C are correct: A accurately lists Huawei's supported authentication algorithms (Null, Simple, MD5, HMAC-MD5, and optionally HMAC-SHA256). C correctly identifies that Huawei supports both area-level and interface-level authentication, where interface authentication takes precedence.

Memory tip: Remember "All Packets Authenticate" - OSPF authentication guards every packet type, not just Hello. And think of areas like separate security zones: each area sets its own rules independently, just like different departments can have different password policies.

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