The device is currently on v15.

To change the boot volume on a BIG-IP system from one installed TMOS version to another, the correct CLI tool is:

switchboot

The correct syntax uses the -b flag:

switchboot -b < volume >

This command marks the specified boot location as the one to be used on the next reboot.

Thus, to boot into HD1.2 which contains 13.1.0.6 , the sequence is:

Mark HD1.2 as the next boot location:

switchboot -b HD1.2

Reboot the system:

reboot

This is the standard and officially supported method for selecting a different installed volume.

Why the other options are incorrect:

A. " tmsh reboot HD1.2 "

There is no such tmsh syntax.

Boot volume cannot be selected by adding a parameter to reboot.

C. switchboot -I HD1.2

The -I flag is invalid. Only -b is used.

D. " tmsh switchboot HD1.2 "

switchboot is not a tmsh command; it is a system-level shell utility.

Therefore, Option B is the correct and valid command sequence.