Get a Packet Capture of a GTP Event

Get a packet capture of a GTP event, such as GTP-in-GTP, to troubleshoot an abnormal GTP packet.
To make it easier to troubleshoot an erroneous GTP packet, you can capture a single GTP packet that triggered any of the following GTP events:
  • GTP-in-GTP
  • End user IP address spoofing
  • Abnormal GTPv1-C, GTPv2-C, and GTP-U messages that have a missing mandatory Information Element (IE), invalid IE, out-of-order IE, invalid header, or unsupported message type
  • Other abnormal GTPv1-C, GTPv2-C, and GTP-U messages
  1. Enable GTP if you haven’t already.
  2. Enable packet capture in a GTP Protection Profile.
    1. Select ObjectsSecurity ProfilesGTP Protection and select an existing profile or Add a new profile.
    2. Select GTP InspectionGTP-C and enable either GTPv2-C Stateful Inspection or GTPv1-C Stateful Inspection to enable the GTP Protection profile.
    3. Select Other Log Settings and enable Packet Capture.
    4. Click OK.
  3. Apply the GTP Protection profile to a Security policy rule that applies to the zone you are protecting.
  4. Commit your changes.
  5. If the Application Command Center (ACC) on your firewall indicates a GTP problem that you want to troubleshoot, select MonitorLogsGTP and look for the GTP packet capture icon ( gtp_pcap_icon.png ) at the beginning of rows that capture troublesome GTP packets. In that row you’ll see the GTP Event Type (such as GTP-in-GTP), the international mobile subscriber identity (IMSI), source and destination IP address of the packet, and other information.
  6. If you want more details to verify the event, click on the gtp_pcap_icon.png to download a packet capture file.
  7. Click Export to export the file to readable format and verify that the details support the GTP event type.
    In this packet capture example, the packet has two headers entitled GPRS Tunneling Protocol; a GTP header inside another GTP header verifies that the GTP-in-GTP event is not a false positive; it’s identified as a GTP-in-GTP attack.

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