Changing the Subnet Mask of a TCP/IP Interface

Resolving The Problem

When trying to change the subnet mask of an interface that has associated routes, message TCP265A is issued even if the interface or TCP/IP is inactive. This change must be made during a period of downtime because the interface must be deactivated. This configuration must be done from the console or from a session to an interface other than the one that must be changed. To change this interface without first removing all of the associated routes, add an interface that is on the same subnet (this is a temporary interface that must be an available one that is not used currently on your network). Activate the new IP address and deactivate the address you want to change. Now all of the routes will be associated with the new interface and, as a result, you can make changes to the old interface. After making the changes, activate this interface and deactivate the temporary interface. Then, delete the temporary interface once it is inactive.

Do the following:

Note: This does not work at releases of OS/400 prior to V5R1M0.