Why some LAN connections fail

Sometimes an incorrectly configured controller description can cause a connection failure.

The cases here involve the incorrect configuration of the adapter address, source service access point (SSAP), or destination service access point (DSAP) parameters.

For more information about how these parameters influence a successful connection, see How LAN devices identify themselves. For other causes of a connection failure, see Which device initiates the connection.

The remote system does not connect:

If your controller description uses dial mode, it is not unusual for the system to receive message CPA58E0 (Controller not replying) or CPA57EF (Contact not successful). Remote systems or controller descriptions that do not vary on can cause one of these messages to appear.

Your system does not connect:

If your controller description uses answer mode, you might receive the message CPI591A (Controller is online, varied off, or not recognized by the local system). There are some things that can cause this message to appear:

• The connection requested by the remote system does not exist on the local system. The local system searches for this connection (that is indicated by combining the local adapter address, the DSAP, and the SSAP) in all varied-on controller descriptions.
• The controller description does not refer to the line description that can answer the call.

Solution:

To correct any of the above problems, do one or more of these steps:

• On either side of the connection, verify that the controller description has the correct combination of adapter address, SSAP, and DSAP.
• Enter the line description that can accept the call into the Switched line list field of the controller description. See Understanding connection establishment for information about the relationship between line descriptions and controller descriptions.
• Vary on the correct controller description (use the Work with Configuration Status (WRKCFGSTS) command to vary on the controller).
• Verify that the local and remote adapters are wired into the network correctly.