This read-write value specifies which physical Cascade switch node, as opposed to just interface or slot, hosts the SSI that this DXI/SNI port's SMDS traffic is multiplexed onto, completing the trio with lportSmdsSsiIf and lportSmdsSsiSlot to fully identify the target SSI location across a multi-node network. An admin sets this correctly during provisioning in multi-node deployments to ensure SMDS traffic gets routed to the right node entirely, not just the right slot or interface on the wrong node. For example, in a network with multiple Cascade nodes, lportSmdsSsiNode pointing to the wrong node number would misdirect this port's SMDS traffic to an entirely different physical switch than intended.