Last Modified: Sep 05, 2026
Affected Product(s):
BIG-IP DNS, GTM, Link Controller, LTM
Known Affected Versions:
16.1.4.2, 16.1.4.3, 16.1.5, 16.1.5.1, 16.1.5.2, 16.1.6, 16.1.6.1, 17.1.2.1, 17.1.2.2, 17.1.3, 17.1.3.1, 17.1.3.2, 17.5.0, 17.5.1, 17.5.1.2, 17.5.1.3, 17.5.1.4, 17.5.1.5, 17.5.1.6, 17.5.1.8
Fixed In:
17.5.1.9, 17.1.3.4
Opened: May 21, 2025 Severity: 3-Major
Big3d high CPU utilization occurs
Big3d high CPU utilization
Large volume of https monitors and monitored resources with SNI configured
None
This fix introduces a new database variable, big3d.ssl.sessionsizemultiplier, to reduce high CPU utilization in big3d caused by thousands of HTTPS monitors with SNI. The SSL session cache size, previously fixed at 4096 entries, is now increased to 16,384 entries by default (multiplier set to 4) to mitigate excessive cache thrashing. This change allows sufficient cache space for unique IP+SNI combinations and decreases CPU usage. For very large resource pools that still experience high CPU, the multiplier can be adjusted up to 32 using: tmsh modify sys db big3d.ssl.sessionsizemultiplier value <4-32>. No reboot or additional fix is necessary for this adjustment.