Bug ID 992865: Virtual server may not enter hardware SYN cookie mode on BIG-IP i11000 and i15000 series appliances

Last Modified: Jul 12, 2023

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

Known Affected Versions:,,, 14.1.4,, 14.1.3

Fixed In:
17.1.0,, 15.1.4

Opened: Feb 11, 2021

Severity: 3-Major


On particular platforms, virtual servers do not correctly enter hardware SYN cookie mode. Software SYN cookie mode still functions correctly.


Software SYN cookies are enabled, this has a performance impact compared to the hardware mode.


-- Virtual server under SYN flood attack. -- One of the following platforms + BIG-IP i11000 series (C123) + BIG-IP i15000 series (D116)



Fix Information

Virtual servers correctly enter hardware SYN cookie mode on all platforms.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips