CPRI Interface Error Alarm

OSS and NOC
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1

Can anyone explain what the CPRI Interface Error alarm indicates?

What are the common root causes and recommended troubleshooting steps?

2

Can you please share the alarm screenshot?

3

CPRI Interface Error means the fronthaul link between the baseband board (BBU) and the radio unit (RRU/RRH/AAU) has lost sync or is erroring — the optical serial link can’t establish or hold the CPRI frame. It usually resolves to one of: loss of signal (LOS), loss of frame/sync (LOF), CPRI line-rate mismatch, or Rx optical power out of range. Cells on the affected radio typically go down with it.

Root causes, physical-first (that’s the order to work them):

  1. Fibre/optical — dirty or damaged LC connector, bent/pinched fibre past its bend radius, loose or disconnected patch cord, too much attenuation (long run, extra splices, wrong attenuator), or Tx/Rx pair swapped. This is the single most common bucket.
  2. SFP module — faulty SFP either end, or wrong SFP: line rate that doesn’t support the configured CPRI option (e.g. 9.8G/10.1G/24.3G), mismatched wavelength, or single-mode vs multi-mode mismatch. Not fully seated counts here too.
  3. Rate / topology config mismatch — configured CPRI line rate or RRU port/topology (star vs chain/ring) doesn’t match the physical cabling.
  4. Radio side — RRU not powered / undervoltage / still rebooting, or RRU optical port HW fault. If the RRU is down, the CPRI error is a symptom, not the cause.
  5. BBU side — baseband board optical port fault, board reset, or RRU cabled to a different port than configured (slot/port mapping wrong).

Troubleshooting steps:

  1. Read the exact alarm sub-reason (which BBU slot/port, which RRU, and whether it’s LOS / LOF / rate mismatch / low Rx). That single field tells you which branch below.
  2. Confirm the RRU is powered and fully booted first — rule out “radio down” masquerading as a link error.
  3. Read Tx and Rx optical power (DDM) on both SFPs. Compare Rx against SFP sensitivity — low or absent Rx points straight at fibre/connector/attenuation.
  4. Reseat and clean both LC connectors, inspect the fibre for damage and bend radius, confirm Tx/Rx aren’t swapped, and swap in a known-good patch cord.
  5. Verify SFP type/rate matches the configured CPRI line rate on both ends, matching wavelength and mode; swap in a known-good SFP.
  6. Check configured CPRI rate and RRU port/topology mapping against the actual cabling; fix any mismatch.
  7. Isolate by swapping: move the RRU to a known-good BBU port, or a known-good RRU onto the same port — that localises it to BBU port vs SFP vs fibre vs RRU.
  8. If everything physical is clean and it still errors, it’s a HW fault: replace in the order SFP → RRU → baseband board, and escalate to vendor TAC with the optical readings and alarm detail attached.

Verification: alarm clears, RRU returns to available, the cells on that radio recover, and no CRC/bit-error counters increment on the fronthaul port. Watch 24h — an intermittent CPRI error that comes and goes is almost always a marginal SFP or a dirty/loose connector, not config.

Tell me the vendor (Ericsson / Huawei / Nokia / ZTE) and I’ll map this to the exact alarm name and the read commands for that BBU.