Last Modified: Dec 18, 2025
Affected Product(s):
BIG-IP LTM
Known Affected Versions:
17.5.0, 17.5.1, 17.5.1.2, 17.5.1.3
Fixed In:
21.0.0
Opened: Aug 26, 2025 Severity: 2-Critical
With Hyper-V platforms, VMBus devices are present due to the virtualization architecture. These devices make use of VMBus channels in the /sys/bus directories. Hyper-V has a reported supported limit of 128 monitored VMBus channels. Patches for non-monitored (low-speed) VMBus channels have caused connectivity problems and eal-intr-thread cores.
Traffic interrupts and eal-intr-thread cores can occur.
-- Use Hyper-V platform -- Use 16 vCPUs and attach >= 7 interfaces -- Use 24 vCPUs and attach >= 6 interfaces
Deploy instances with <= 3 interfaces on Hyper-V platforms.
Regardless of combinations of vCPU and interface counts, traffic can be passed and eal-intr-thread cores are limited. VMBus channels correspond with device queues so the 128 monitored VMBus channel limit forces queue-sharing and impacts performance. To avoid losing performance, deploy instances with fewer interfaces.