A CN Subnet consists of CN servers in Core Cells. The working CN in a Core Cell is only one, but spare one should be prepared for high availability. IP/Port of all CNs within the Core Cell Network (CCN) must be opened to each other because they try to connect to the others from the outside of the Core Cell. (This connection information can be received from Baobab operators.) The internal communication with other subnets in the Core Cell requires to open default port (32323: default Klaytn P2P port number) in order to connect to PNs of the PN Subnet. Furthermore, it is necessary to open other ports such as the CN monitoring port (61001) for the monitoring server and the SSH port (22) for the management purpose. If the multichannel feature is used, another port (32324: default multichannel port) should be opened as well.