Bug ID 660252: Enabling SYN-Cookies may severely impact DNAT performance

Last Modified: Sep 14, 2023

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

Known Affected Versions:
13.1.0, 13.1.0.1, 13.1.0.2, 13.1.0.3, 13.1.0.4, 13.1.0.5, 13.1.0.6, 13.1.0.7, 13.1.0.8, 13.1.1, 13.1.1.2, 13.1.1.3, 13.1.1.4, 13.1.1.5, 13.1.3, 13.1.3.1, 13.1.3.2, 13.1.3.3, 13.1.3.4, 13.1.3.5, 13.1.3.6, 13.1.4, 13.1.4.1, 13.1.5, 13.1.5.1, 14.0.0, 14.0.0.1, 14.0.0.2, 14.0.0.3, 14.0.0.4, 14.0.0.5, 14.0.1, 14.0.1.1, 14.1.0, 14.1.0.1, 14.1.0.2, 14.1.0.3, 14.1.0.5, 14.1.0.6, 14.1.2, 14.1.2.1, 14.1.2.2, 14.1.2.3, 14.1.2.4, 14.1.2.5, 14.1.2.6, 14.1.2.7, 14.1.2.8, 14.1.3, 14.1.3.1, 14.1.4, 14.1.4.1, 14.1.4.2, 14.1.4.3, 14.1.4.4, 14.1.4.5, 14.1.4.6, 14.1.5, 14.1.5.1, 14.1.5.2, 14.1.5.3, 14.1.5.4, 14.1.5.6

Opened: Apr 24, 2017

Severity: 2-Critical

Symptoms

Low number of connections per second and lower throughput performance. Log messages: Syncookie embryonic connection counter ###### exceeded sys threshold ###### Syncookie HW mode activated, server = x.x.x.x:x, HSB modId = 1

Impact

Low number of connections per second and lower throughput performance.

Conditions

Using DNAT with SYN-Cookies enabled, or non-maximum value for SYN-cookie threshold.

Workaround

There are three workarounds: -- Use a different NAT method. -- Disable SYN-cookies. -- Increase the SYN-cookie threshold to the maximum value.

Fix Information

None

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips