Malformed and unexpected packets

An OSPF packet is considered malformed and is discarded if any of the following are present in the packet:

• Incorrect version in the OSPF packet header.
• Incorrect packet type in the OSPF header.
• Incorrect length value in the OSPF packet header.
• Incorrect checksum in the OSPF packet header.
• Incorrect LSA type in an LSA header.
• Incorrect length value in an LSA header.
• Incorrect checksum in an LSA header.
• Incorrect LSA age field in an LSA header.
• Incorrect LSA scope value in an LSA header.
• Incorrect prefix length value in an LSA that includes address prefixes.
• Incorrect value for the number of entries in a packet or LSA. For example, a bad number of LSAs value in a Link State Update packet, a bad number of links value in a Router LSA, or a bad number of prefixes value in a Link LSA or Intra-Area Prefix LSA.

An OSPF packet is considered unexpected and is discarded if any of the following are present in the packet:

• Unexpected AS External LSA received over an interface that is attached to an OSPF stub area.
• Unexpected AS External LSA received over a virtual link.
• Unexpected AS Scope LSA received over an interface that is attached to an OSPF stub area.