Planning for static VIPA takeover and takeback

Because a VIPA is associated with a z/OS® TCP/IP stack and is not associated with a specific physical network attachment, it can be moved to a stack on any image in the sysplex or even to any z/OS TCP/IP stack as long as the address fits into the network configuration. Moving a static VIPA can be done manually by an operator or by customer-programmed automation. Movement of the static VIPA allows other hosts that were connected to the primary stack to reestablish connections with a backup TCP/IP stack using the same VIPA. After the primary TCP/IP stack has been restored, the reassigned VIPA address can be moved back.

Consider the following items when backing up and restoring a z/OS TCP/IP stack:

• All connections on the failing host will be disrupted.
• The client can use any ephemeral port number when reestablishing the connection to the backup server.
• Having a different port number for the backup and primary server is not recommended. For example, if the primary FTP used port 21 and the backup FTP used port 1021, when backing up and restoring a z/OS TCP/IP stack, the client would have to know whether to use port 21 or 1021.

If you are deploying both static VIPA and OSA-Express QDIO, see VIPAs, OSA-Express QDIO, and Spanning Tree Protocol to determine whether or not network bridge or switch configuration settings might potentially impact the environment for VIPA takeover and takeback.