5G NAS error codes and cause values

5GMM and 5GSM Cause Codes

When the network rejects a registration or PDU session request, it includes a cause value that explains the reason for rejection. These codes are defined in 3GPP TS 24.501 and are essential for troubleshooting. 5GMM cause values (for registration and mobility management) include code 3 for illegal UE, code 11 for PLMN not allowed, code 12 for tracking area not allowed, and code 20 for MAC failure. 5GSM cause values (for session management) include code 26 for insufficient resources and code 27 for missing or unknown DNN.