Bug ID 1085837: Virtual server may not exit from hardware SYN cookie mode

Last Modified: Mar 11, 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,,,, 15.0.0, 15.0.1,,,,, 15.1.0,,,,,, 15.1.1, 15.1.2,, 15.1.3,, 15.1.4,, 15.1.5,, 15.1.6, 16.0.0,, 16.0.1,,, 16.1.0, 16.1.1, 16.1.2,,, 16.1.3,,,, 17.0.0,,

Fixed In:

Opened: Mar 09, 2022
Severity: 3-Major


Once a virtual server enters hardware SYN cookie mode it may not exit until a TMM restart.


-- Virtual servers in hardware SYN cookie mode do not receive TCP SYN packets. -- The limited number of possible TCP MSS values may have a light performance impact.


-- On B2250 and B4450 platforms. -- A condition triggers SYN cookie mode and then goes back to normal.


Disable hardware SYN cookie mode on the affected objects.

Fix Information

Virtual servers properly exit hardware SYN cookie mode.

Behavior Change