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Sandbox Lab advanced 30 min3 graded questions

Debug a Failed UE Registration

A newly provisioned UE keeps failing to attach while others work fine. Use AUSF and UDM tooling to find the misconfiguration, fix it, and verify registration succeeds.

Scenario
A customer support ticket lands on your desk: "IMSI 999700000000099 fails to attach. All other SIMs on the same tower work fine." You have sandbox-level access to the 5G core. The Open5GS network is up, most UEs are fine, but this particular IMSI cannot register. Your job: 1. Reproduce the failure. 2. Find the root cause by reading AUSF logs and UDM subscriber data. 3. Fix the config. 4. Verify the UE now registers successfully. Along the way you will see 5G-AKA fail with a MAC failure — and learn the difference between MAC failure and Synch failure (two very different root causes).

What you'll do

  1. Attempt to register the failing UE
  2. Check AUSF logs to find the auth failure cause
  3. Inspect the UDM subscriber record for 999700000000099
  4. Fix the subscriber key in the UDM
  5. Re-attempt registration

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