Specifies the per rule mask for the destination MAC addres field as defined in swEgressACLEtherRuleDstMacAddress object. The value of this object when not in use is the corresponding mask in the profile mask. Once the value of this object is modified, the per rule mask will take effect.
Sources for this description
D-Link official switch MIBsD-Link MIB copies (LibreNMS/Observium Community)