All / some UL values under certain Nodes have already been “claimed” or “reserved” by certain Standards yet no indication of this is given in the Registers.

For example, not all of the possible UMID ULs (under UMID Nodes) have been listed in the Registers due to the huge number of combinations.

So, it is necessary to take a little care when choosing UL values for new entries – as long as a sensible location is chosen then there should not be an issue.