Indicate the mask to be logical-AND with the destination address before being compared to the value in the swL3IpStaticRouteDest field. For those systems that do not support arbitrary subnet masks, an agent constructs the value of the swL3IpStaticRouteMask by reference to the IP Address Class. Any assignment (implicit or otherwise) of an instance of this object to a value x must be rejected if the bitwise logical-AND of x with the value of the corresponding instance of the swL3IpStaticRouteDest object is not equal to swL3IpStaticRouteDest.
Sources for this description
D-Link official switch MIBsD-Link MIB copies (LibreNMS/Observium Community)Netdisco MIB archive copies