A composite network node (CNN) is composed of a VTAM® interchange node and any NCPs that it owns. In an APPN network, it functions as a network node and appears to the APPN network as a single node. A composite network node is defined by coding the HOSTSA start option, the NODETYPE start option as NN, and by activating an NCP from that VTAM.

The composite network node can be attached to other APPN nodes and also to subarea nodes. In a composite network node where all external connections are APPN connections, the HOSTSA value is not used in communication outside the node. If the composite node is connected to other nodes by subarea connections, the HOSTSA value is used in communication with the subarea network.