Bug ID 1304189: Duplicate SYNs to a mirrored FastL4 virtual may result in connection failures

Last Modified: May 29, 2024

Affected Product(s):
BIG-IP LTM(all modules)

Known Affected Versions:, 15.1.9,, 15.1.10,,,,,,,,, 16.1.4,,,,,,

Fixed In:

Opened: Jun 01, 2023

Severity: 3-Major


If a duplicate SYN arrives on a connection before the SYN/ACK is processed and the connection is pushed into PVA, then when it is later evicted from PVA it may stop passing traffic and be reset with the RST cause "Handshake Timeout".


Connection will stop passing traffic and resets when they are evicted from PVA.


- PVA enabled - Mirroring enabled - Duplicate SYNs on the network


Perform one of the following as a workaround: - Disable PVA - Disable mirroring - Modify sys db tm.fastl4_ack_mirror value to Disable - Modify sys db tm.fastl4_mirroring_taciturn value to Enable.

Fix Information


Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips