Troubleshooting DLSw 233segment. After both sides have established a correct route, the TCP connectioncan be created.Unable to Establish aDLSw CircuitSymptomA DLSw circuit cannot be correctly established. The display dlsw circuitcommand shows that the virtual circuit cannot come into CONNECTED state.AnalysisMany reasons can cause circuit establishment failure.■ A TCP connection with the peer end must be successfully established first.■ If a TCP connect can be successfully established but circuit establishment fails,the problem usually lies in the cooperation between the router and the SNAdevice, mainly with SDLC configuration.Solution1 First enable the SDLC debugging, and check whether the SDLC interface canreceive/forward frames normally by executing the display interface command. Ifthe interface cannot receive/forward frames correctly, possible causes are incorrectencoding scheme, baud rate or clock configuration on the interface. Modify theinterface configuration parameters of the router or adjust the configurationparameters of the SDLC device.2 If frames can be received and forwarded correctly, examine whether theconfiguration of the PU type is correct. Use the sdlc xid command to configurethe XID and change the configuration of the PU type.3 If the PU type is correct, use the display dlsw circuit verbose command to checkwhether the virtual circuit can enter the CIRCUIT_EST state. If not, the MACaddress of the SDLC peer is not correctly configured. Use the sdlc mac-mapremote command to modify the configuration parameters.4 If the circuit can reach the CIRCUIT_EST state, but cannot reach the CONNECTEDstate, this means that the configuration of the SDLC on the router does not matchthat of the SNA devices. Check the configuration of the SDLC devices on bothsides and the configuration of the router. For example, check whether the XID ofthe SNA device is properly configured (PU2.1), and whether the XID of the routeris properly configured (PU2.0). If all these configurations correct, check whetherthe SDLC line on the primary SDLC device side (such as the AS/400 or S390) isactivated. Sometimes the SDLC line needs to be activated manually.
