Cisco ASA Audit Event: 209004

209004: Invalid IP fragment

Cisco ASA is a security device that provides the combined capabilities of a firewall, an antivirus, and an intrusion prevention system. It also facilitates virtual private network (VPN) connections. It helps to detect threats and stop attacks before they spread through the network.

Message: %ASA-4-209004: Invalid IP fragment,size=bytes exceeds maximum size=bytes:src =source_address,dest =dest_address,proto=protocol,id =number.

Event 209004 is generated when an IP fragment is malformed. The total size of the reassembled IP packet would have exceeded the maximum possible size of 65,535 bytes. The message contains information on the:

  • Actual size of the IP fragment.
  • Maximum size of an IP fragment.
  • Source and destination IP addresses.
  • Protocol.
  • Identifier.

How could you resolve this situation?

If the message keeps recurring, it might denote an intrusion event in progress. Contact the remote peer administrator or upstream provider.

Cisco ASA Auditing Tool

EventLog Analyzer is a comprehensive log management software with which you can centrally collect, analyze, and manage logs from all the different log sources in your network. You also get reports and alerts on your network security, making it a power-packed IT security tool.