IST1774I OPTIMAL CNN ROUTE NOT CHOSEN - ENTRY/EXIT SUBAREA MISMATCH
IST1775I CNN ENTRY SUBAREA = entry_subarea   CNN EXIT SUBAREA = exit_subarea
IST664I REAL  OLU=luname1       REAL  DLU=luname2
IST889I SID = session_id
IST314I END

• The origin LU may be either the PLU or SLU. The same applies for the destination LU. If the origin or destination LU name is unknown, VTAM displays ***NA***.

• sessid is a unique identifier for the session. If the session ID is unknown, VTAM displays ***NA***.

• A CNN Route is not optimal if the following conditions are both true:
  • The chosen CNN entry and exit TG subareas do not match.
  • Another active TG to the network node is found that has the same characteristics as the chosen entry TG and the same subarea as the CNN exit TG.
• The reason a nonoptimal route might be chosen is one of the following:
  • The topology of the CNN is not known by the APPN topology and route selection process.
  • The route was calculated by a non-VTAM node that does not support the use of subarea numbers in route calculation.
• The following figure is an example of a configuration:
  Figure 1. Sample configuration

  
• In this figure, the CNN is composed of VTAM2, NCP1, and NCP2. The subarea of NCP1 is the CNN entry TG subarea and the subarea of NCP2 is the CNN exit TG subarea. A session is started between APPL1 (PLU) and LU2 (SLU). If the adjacent network node (NN1) chooses to use TG1 instead of TG2, then the IST1774I message group will appear on VTAM2.
  Note: The APPN node that picked the CNN entry TG (NN1 in the above configuration) is the NNS of the PLU, which may or may not be a VTAM. In addition, the NNS of the PLU may or may not be directly adjacent to the CNN.

• This message follows IST1774I and indicates the CNN entry subarea and the CNN exit subarea.
• entry_subarea is the decimal subarea of the node in the CNN where the BIND entered the CNN from the PLU.
• exit_subarea is the decimal subarea of the node in the CNN where the BIND exited the CNN to the SLU.