The SG2428P running firmware version 5.30.7 does not support "show ddm status".

This is the same for the SG2210P/MP running firmware version 3.0.11 (HW v3)

Most of the other Omada range switches do support this, including the SG2452LP v1.0 - its big brother. 

Could the show DDM status be included in these switches.

Regards

Stephen

Senior Network Engineer