Last Modified: Jul 18, 2026
Affected Product(s):
BIG-IP LTM
Known Affected Versions:
11.5.1, 11.5.1 hf1, 11.5.1 hf2, 11.5.1 hf3, 11.5.1 hf4, 11.5.1 hf5, 11.5.1 hf6, 11.5.1 hf7, 11.5.1 hf8, 11.5.1 hf9, 11.5.1 hf10, 11.5.1 hf11, 11.5.2, 11.5.2 hf1, 11.5.3, 11.5.3 hf1, 11.5.3 hf2, 11.6.0, 11.6.0 hf1, 11.6.0 hf2, 11.6.0 hf3, 11.6.0 hf4, 11.6.0 hf5, 11.6.0 hf6, 11.6.0 hf7, 11.6.0 hf8, 11.6.1, 11.6.1 hf1, 11.6.1 hf2, 11.6.2, 11.6.2 hf1
Fixed In:
12.0.0, 11.6.3, 11.5.4
Opened: Jun 17, 2014 Severity: 3-Major Related Article:
K17011
TCP syncookie and Selective NACK (profile option) causes traffic to be dropped.
Traffic might be dropped.
This occurs when the following conditions are met: -- Selective NACK enabled in TCP profile. -- TCP syncookie mode. -- No Selective NACK option in TCP options from client SYN.
Disable Selective NACK option in TCP profile.
TCP syncookie and Selective NACK (profile option) now works correctly.