Last Modified: Aug 19, 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, 11.5.4, 11.5.4 hf1, 11.5.4 hf2, 11.5.4 hf3, 11.5.4 hf4, 11.5.5, 11.5.6, 11.5.7, 11.5.8, 11.5.9, 11.5.10, 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, 11.6.3, 11.6.3.1, 11.6.3.2, 11.6.3.3, 11.6.3.4, 11.6.4, 11.6.5, 11.6.5.1, 11.6.5.2, 11.6.5.3
Fixed In:
12.0.0
Opened: Jan 22, 2015 Severity: 3-Major Related Article:
K16736
BIG-IP can experience sudden and permanent traffic interruption, impacting all traffic through TMM.
The HSB's transmit ring becomes stuck. This requires a TMM restart in order to clear.
With TCP Segmentation Offload (TSO) enabled, it is possible to fill up the High-Speed Bridge (HSB) transmit ring, resulting in a stuck transmit ring. The exact conditions under which this occurs is unknown, but it requires sudden transmission of a number of large packets that require TSO in order to result in a full transmit ring.
Disable TSO. This can be done using the following steps: 1. tmsh modify sys db tm.tcpsegmentationoffload value disable 2. bigstart restart tmm. If TSO is not disabled, three related fixes are needed to fully address the issue: -- ID 466260, covered in SOL15953: TMM may produce a core file with the 'Assertion we always have room in tx ring! failed' error message. -- ID 502238, covered in SOL16736: The BIG-IP system may lose connectivity and fail to process all traffic through TMM if the HSB is overloaded. -- ID 509782, covered in SOL16780: The BIG-IP system may drop TSO packets. The Solutions are available here: -- https://support.f5.com/kb/en-us/solutions/public/15000/900/sol15953.html -- https://support.f5.com/kb/en-us/solutions/public/16000/700/sol16736.html -- https://support.f5.com/kb/en-us/solutions/public/16000/700/sol16780.html
Three related fixes are needed to fully address the issue: -- ID 466260, covered in SOL15953: TMM may produce a core file with the 'Assertion we always have room in tx ring! failed' error message. -- ID 502238, covered in SOL16736: The BIG-IP system may lose connectivity and fail to process all traffic through TMM if the HSB is overloaded. -- ID 509782, covered in SOL16780: The BIG-IP system may drop TSO packets. The Solutions are available here: -- https://support.f5.com/kb/en-us/solutions/public/15000/900/sol15953.html -- https://support.f5.com/kb/en-us/solutions/public/16000/700/sol16736.html -- https://support.f5.com/kb/en-us/solutions/public/16000/700/sol16780.html