Bug ID 1975297: TMM may fail to start up with max number of interfaces for Azure instances <= 16 vCPUs

Last Modified: Dec 06, 2025

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

Known Affected Versions:
17.5.0, 17.5.1, 17.5.1.2, 17.5.1.3

Opened: Jul 01, 2025

Severity: 3-Major

Symptoms

There are "vmbus_open subchannel failed: -12" kernel errors for uio module, uio_hv_generic. These errors prevent the TMM module from finishing initialization.

Impact

Azure VM is unable to reach Active state.

Conditions

-- Using VE Azure -- Using Azure instances with <= 16 vCPUs

Workaround

Use an Azure instance with more RAM. For example, F8s_v2 has 16 GiB of RAM and has a total limit of 4 interfaces. Instance size, E8ds_v5, has 64 GiB of RAM and can reach Active state with 4 interfaces.

Fix Information

None

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips