Bug ID 659899: Rare, intermittent system instability observed in dynamic load-balancing modes

Last Modified: May 29, 2024

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

Known Affected Versions:
11.5.4, 11.6.0, 11.6.1, 11.6.2, 12.0.0, 12.0.0 HF1, 12.1.0 HF1, 12.0.0 HF2, 12.1.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.1 HF1, 12.1.1 HF2, 12.1.2 HF1, 12.1.2 HF2, 12.1.0, 12.1.1, 12.1.2, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1

Fixed In:
13.1.0, 12.1.3, 11.6.3, 11.5.5

Opened: Apr 21, 2017

Severity: 2-Critical

Related Article: K10589537


The dynamic pool member load-balancing modes require a precision measurement of active connection counts and/or rates. Rare, intermittent system instability has been observed in dynamic pool member selection when a new connection arrives. TMM may restart, leaving a core file.


TMM restarts and leaves a core file. Traffic disrupted while tmm restarts.


LTM pool configured to use a dynamic load-balancing mode ('ltm pool NAME load-balancing-mode MODE' where MODE is one of the dynamic load-balancing modes, such as dynamic-ratio-member, least-connections-node, predictive-node, etc.). The dynamic modes use the session database to share data among all TMM instances, and under extremely rare conditions, the session database may become unreliable.



Fix Information

The dynamic load-balancing modes are now more tolerant of errors from the underlying session database.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips