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

Last Modified: Jul 17, 2024

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

Known Affected Versions:
14.1.5, 14.1.5.1, 14.1.5.2, 14.1.5.3, 14.1.5.4, 14.1.5.6, 15.1.5.1, 15.1.6, 15.1.6.1, 15.1.7, 15.1.8, 15.1.8.1, 15.1.8.2

Fixed In:
17.1.0, 15.1.9

Opened: Jun 23, 2022

Severity: 3-Major

Symptoms

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.

Impact

Service degradation.

Conditions

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

Workaround

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

Fix Information

The SYN cookie hash algorithm is correctly selected on all TMMs.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips