Chapter 5 FortiOS Carrier : Troubleshooting : GTP packets are not moving along your network
  
GTP packets are not moving along your network
When GTP packets are not getting to their destination, this could be caused by any one of a number of issues. General troubleshooting principals apply here.
The following sections provide some suggestions on how to troubleshoot this issue:
• Attempt to identify the section of your network with the problem
• Ensure you have an APN configured
• Check the logs and adjust their settings if required
• Check the routing table
• Perform a sniffer trace
• Generate specific packets to test the network