Bug ID 1121085: Some valid connections may get rejected in hardware SYN cookie mode

Last Modified: Jan 20, 2023

Bug Tracker

Affected Product:  See more info
BIG-IP TMOS(all modules)

Known Affected Versions:
14.1.0,,,,,, 14.1.2,,,,,,,,, 14.1.3,, 14.1.4,,,,,,, 14.1.5,,,, 15.1.0,,,,,, 15.1.1, 15.1.2,, 15.1.3,, 15.1.4,, 15.1.5,, 15.1.6,, 15.1.7, 15.1.8,

Opened: Jun 23, 2022
Severity: 3-Major


Due to an algorithm mismatch in software and hardware, valid TCP connections may get rejected with "No flow found for ACK' reset-cause when the hardware SYN cookie mode is active.


Service degradation.


- BIG-IP iSeries appliances with ePVA support and the B2250 and B44xx VIPRION blades. - Hardware SYN cookie mode is activated.


- Disable the hardware SYN cookie mode globally. - After a reboot, restart the TMM for an additional time.

Fix Information


Behavior Change