Port reuse on a GlobalProtect connections causing TCP handshake... - Knowledge Base - Palo Alto Networks

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

2845

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

GlobalProtect Portal

TCP

Decryption

PAN-OS

Strata

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.

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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