Port reuse on a GlobalProtect connections causing TCP handshake failure and connection failures

Port reuse on a GlobalProtect connections causing TCP handshake failure and connection failures

1036
Created On 10/11/23 16:59 PM - Last Modified 06/24/24 20:41 PM


Symptom


  • Unable to connect to the Portal/GW from linux machines
  • TCP Handshake failure and "[TCP Port numbers reused]" seen in the SYN packets on wireshark captures with no SYN+ACK back.
image (38).png
 
 
 

Environment


  • Palo Alto Firewalls
  • Supported PAN-OS
  • GlobalProtect

Cause


A new SYN packet reusing the same tuple (ip/port etc) arrives on the firewall when the the previous session is not yet cleared. This causes the old session to be refreshed, but not reused causing interruption.

Resolution


Add a CLI command to clear the old session immediately and avoid issues 
>debug proxy fast-session-delete enable yes

 
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