A network node capable of APPN multiple network connectivity, also known as a border node, can maintain CP-CP connectivity with a network node with a different NETID. APPN topology information does not cross the border node connection or APPN subnetwork boundary, but search requests can, and an LU-LU session can be set up. An APPN subnetwork boundary is assumed by VTAM® when a border node is connected to a network node (or border node) with a different network identifier.

An APPN subnetwork boundary can also be explicitly defined through system definition. This way, border nodes can be used to create subnetwork boundaries to adjacent network nodes (or border nodes) with the same network identifier.

For further information about border nodes, see APPN multiple network connectivity.