Unknown-mme-ue-s1ap-id -

| Data Source | What to Look For | |-------------|------------------| | | Find the MME UE S1AP ID in the failing message. Search backwards for a UE CONTEXT RELEASE COMPLETE or UE CONTEXT RELEASE REQUEST for the same ID. | | eNB Logs | Look for S1AP: Unknown MME UE S1AP ID or No active UE context for MME ID X . | | MME Logs | Check timestamps of the last successful INITIAL CONTEXT SETUP for that UE. See if a RESET message was sent/received. |

MME -> eNB: UE CONTEXT RELEASE COMMAND (MME UE S1AP ID = 12345) eNB -> MME: ERROR INDICATION (Cause: unknown-mme-ue-s1ap-id) Root cause: eNB log shows [ERROR] UE context 12345 already freed due to RRC timeout 10ms earlier . unknown-mme-ue-s1ap-id

The eNB maintains a local mapping between its eNB UE S1AP ID and the MME’s MME UE S1AP ID . If the MME sends a message (e.g., UE CONTEXT RELEASE COMMAND , DOWNLINK NAS TRANSPORT ) with an ID that the eNB has no record of, the eNB rejects it with this cause. | Data Source | What to Look For