Last Modified: Feb 06, 2026
Affected Product(s):
BIG-IP LTM
Known Affected Versions:
17.1.0, 17.1.0.1, 17.1.0.2, 17.1.0.3, 17.1.1, 17.1.1.1, 17.1.1.2, 17.1.1.3, 17.1.1.4, 17.1.2, 17.1.2.1, 17.1.2.2, 17.1.3, 17.1.3.1
Opened: Feb 04, 2026 Severity: 3-Major
When in-TMM monitoring is enabled (sys db bigd.tmm value enable), health monitors may mark pool members down earlier than the configured timeout value. The issue is intermittent and the failure rate increases with higher TMM instance counts: 2 TMM instances: ~25% failure rate (1 failure out of 4 tests) 4 TMM instances: ~50% failure rate (1 failure out of 2 tests)
Unpredictable and inconsistent failure detection timing causes timing unpredictability, the actual timeout can vary significantly from expected.
In-TMM monitoring enabled with HTTP/HTTPS/TCP monitors. sys db bigd.tmm value "enable" Multiple tmm instances are present.
Disable in-TMM monitoring to revert to legacy bigd monitoring:
None