The below SQL script should re-enable:
INSERTINTO dbo.[NodeSettings] (NodeID, SettingName, SettingValue)
SELECT n.NodeID,'NeedsInventory','MulticastRouting'
FROM Nodes n
WHERE n.ObjectSubType ='SNMP'AND n.NodeID NOTIN(SELECT NodeID FROM dbo.[NodeSettings] WHERE SettingName ='NeedsInventory'AND SettingValue ='MulticastRouting')