Bug ID 978953: The value of the sys db variable vlan.backplane.mtu intermittently out-of-sync with the value of the MTU of the kernel interface tmm_bp during the initial boot up

Last Modified: Jan 20, 2023

Bug Tracker

Affected Product:  See more info
BIG-IP All(all modules)

Known Affected Versions:
14.1.0,,,,,, 14.1.2,,,,,,,,, 14.1.3,, 14.1.4,,,,,,, 14.1.5,,,, 15.1.0,,,,,, 15.1.1, 15.1.2,, 15.1.3,, 15.1.4,, 15.1.5,, 15.1.6,, 15.1.7, 15.1.8,

Opened: Jan 06, 2021
Severity: 3-Major


During the initial boot of the device the MTU of the tmm_bp kernel interface is out-of-sync with the value of sys db vlan.backplane.mtu as well as out-of-sync with the MTU displayed by the following command: tmsh show /net vlan all-properties -hidden. tmsh list net vlan tmm_bp all-properties -hidden. Additionally, running the following command: modify sys db vlan.backplane.mtu value <some value> (within the range accepted), and saving the configuration change does not last through a reboot.


When the values are seen at non-sync, after the modification of the backplane vlan mtu and saving the config, changing the mtu config value does not last through a reboot.


This issue occurs on the first boot intermittently.


Rebooting the device resolves the issue

Fix Information


Behavior Change