Bug ID 622856: BIG-IP may enter SYN cookie mode later than expected

Last Modified: Sep 13, 2023

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

Known Affected Versions:
11.5.4, 11.5.5, 11.6.1, 11.6.2, 11.6.3,

Fixed In:
13.0.0, 12.1.2 HF1,, 11.5.6

Opened: Oct 14, 2016

Severity: 2-Critical


BIG-IP entry to SYN cookie mode may not occur even though traffic pattern would dictate that it should.


BIG-IP does not enter SYN cookie mode at the expected time.


Verified accept enabled on a Virtual IP. Large volume of traffic being processed by BIG-IP.


Disable verified accept on all VIP TCP profiles.

Fix Information

BIG-IP correctly enters SYN cookie mode when traffic pattern dictates that it should.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips