Indicate the mask to be logical-ANDed with the destination address before being compared to the value in the sleRouteDstAddress field. For those systems that do not support arbitrary subnet masks, an agent constructs the value of the sleRouteDstMask by determining whether the value of the correspondent sleRouteDstAddress field belong to a class-A, B, or C network. If the value of the sleRouteDstAddress is 0.0.0.0 (a default route), then the mask value is also 0.0.0.0. It should be noted that all IP routing subsystems implicitly use this mechanism.