143-130 · Question #96
A Brocade DCX 8510 customer with a single link cascaded FICON fabric (20 km distance) running at 8 Gbps experiences an increasing number of bit failures. The customer receives 10 CRC errors per…
The correct answer is D. Verify that all physical components in the ISL data path are functioning properly. See the full explanation below for the reasoning.
Question
A Brocade DCX 8510 customer with a single link cascaded FICON fabric (20 km distance) running at 8 Gbps experiences an increasing number of bit failures. The customer receives 10 CRC errors per hour. Which action should be taken?
Options
- AEnable Forward Error Correction (FEC).
- BEnable BCR Buffer Credit Recovery.
- CReset the counters and monitor the ISL carefully.
- DVerify that all physical components in the ISL data path are functioning properly.
How the community answered
(35 responses)- A3% (1)
- B6% (2)
- C9% (3)
- D83% (29)
Community Discussion
7
Fatima Z.Jun 27, 2026D is your answer, and here is the sticky way to remember it, think "CRC Screams Check Reality Carefully" because when you see bit errors and CRC failures piling up on a FICON ISL, that is always a physical layer problem first, meaning you go verify your SFPs, cables, and every physical component in that data path before you touch any software setting. FEC and BCR might sound tempting but those are band-aids, and resetting counters is just hiding the wound.
Ola B.Jun 29, 2026Good mnemonic but do not forget that dirty or misaligned fiber connectors are statistically the most common culprit in CRC-heavy FICON ISLs, so clean the connectors on both sides of every suspect cable before you even pull an SFP.
Haruki E.Jun 18, 2026D is the right call here, and the reasoning is straightforward once you think about what CRC errors actually tell you. A CRC error means the receiving end calculated a different checksum than what the sender transmitted, which points directly at signal corruption somewhere in the physical data path, not a software or configuration issue. On a 20 km single-link FICON ISL running at 8 Gbps, you have a long stretch of glass with multiple connectors, patch panels, and SFPs that can all introduce bit errors if any one of them is dirty, damaged, or marginal. FEC in option A is a coping mechanism, not a fix, and enabling it without finding the root cause leaves a degraded link in production under a FICON workload where data integrity is non-negotiable. BCR in option B addresses credit starvation, not corruption, so that is solving a completely different problem. The right move is to clean and inspect every connector end-face on that ISL, swap suspect SFPs, check the optical power levels with a light meter, and trace the fiber path for any tight bends or damaged segments before you declare the link healthy.
Orla P.Jun 27, 2026D is right, bad CRC at that rate points to a failing physical component in the path.
Ola B.Jun 25, 2026D is the right call here. CRC errors point to physical layer problems, so before you touch any software settings or enable features like FEC, you need to walk the entire ISL data path, SFPs, cables, connectors, and patch panels, because a single dirty or failing component at 20 km can produce exactly this kind of creeping bit error pattern.
Luis F.Jun 15, 202610 CRC errors per hour is borderline, reset and watch before touching anything.
Haruki E.Jun 16, 2026Luis, appreciate the input, but D is the right call here because 10 CRC errors per hour on a production link consistently points to a physical layer fault, bad SFP or degraded cable, that a reset will not fix and that will only get worse under traffic load. Passive watch-and-wait just delays the inevitable port flap during peak hours.