3Com NBX 100 Administrator's Manual page 335

All NBX systems that ship from the factory with software release R4.2 or
any later release, include a license for the software version that is shipped
with the system.
Upgrading to R4.2 From a Previous Release
To upgrade an NBX system to release R4.2 you must first upgrade to
release R4.1.
Upgrading From R4.1.14 and Prior Releases
If your NBX system software is release R4.1.14 or a previous release, you
cannot enter the license key for R4.2 before you upgrade because the
NBX system software will not recognize the R4.2 license as valid.
Use these steps to upgrade to R4.2:
1 Upgrade to R4.2 in the usual way.
2 Reboot to R4.2.
3 When you see the warning message that indicates you must install a
license, click the License button and install the R4.2 license.
If you decide not to install the R4.2 license key, you can click the Reboot
button and select a different release.
Upgrading From R4.1.15 and Later Versions
If you are running R4.1.15 or a later release of R4.1, you can enter the
R4.2 license key and then upgrade. When you enter the license key, the
NBX system software accepts the license key as valid for an unknown
feature. When you upgrade and reboot to R4.2, the license for R4.2 takes
effect.
Upgrading From Release 4.2
If you are running R4.2 and you upgrade to a new NBX software version,
the final step is to reboot the NBX system specifying the new release. At
that time, the NBX software verifies that you have the proper license
installed. If you have installed the license prior to the reboot, the upgrade
is completed.
If you have not installed the correct license prior to the reboot phase of
the upgrade, the NBX system provides a warning message and guidance
on the appropriate action for you to take.
Software Upgrade 335