What needs to be checked when the test case aborts with the error “Error: Unable to open session with DUT”?

What needs to be checked when the test case aborts with the error “Error: Unable to open session with DUT”?

1) ATTEST has flexibility to support custom type of sessions. For example, the DUT may require a sequence commands to be executed in the DUT CLI before the CLI module is enabled.

2) In the procedure callback_user_defined_open_session, the user is provisioned to open a conventional telnet/serial connection.The user can then perform additional configuration by integrating the user defined commands in DUT_USER_DEFINED_OPEN_SESSION API provided in the same mapping file, or he can even write his own expect commands.

3) If the user wishes to opt for the custom type of open session, the ‘DUT custom open session’ option must be set to ‘Enable’ in ATTEST Configuration Manager-> Protocol Options