Knowledge Base

Symptom

When using some FEC (Forward Error Correction) standards, the link between the switch and storage does not get online. Users may observe the following issues:

• Link Not Coming Online:
  1. The link status in the switch management interface shows as disconnected or down.
  2. The link indicator lights on the switch or storage device may not be lit.
• Inability to Access Storage:
  1. Users cannot access the storage devices over the network.
  2. Data transfer and access operations fail.
• Error Messages or Alarms:
  Error messages such as "Link Down" or "Link Not Online" appear in the management interface.
• Performance Issues:
  Unstable or intermittent link leads to slower data transfer rates or interruptions.

Conditions When the Problem Occurs

This issue is related to an improper configuration of FEC on the switch side while using different types of DAC (Direct Attach Cable).

Solution

To ensure proper connectivity between your switch and storage using DAC, follow these guidelines based on the type of DAC and FEC settings:

• DAC with RS-FEC (0b):
  1. Cable Length: Usually 3-5 meters.
  2. FEC Setting: The link will be up only if the switch side is configured as FEC108.
• DAC with FC-FEC (0c):
  1. Cable Length: Usually 1-3 meters.
  2. FEC Setting: The link will be up if the switch side is configured as either FEC74 (default in most cases) or FEC108.
• DAC with FEC-NONE (0d):
  1. Cable Length: Usually also 1-3 meters.
  2. FEC Setting: The link will be up if the switch side is configured as either FEC-NONE, FEC74, or FEC108.

By ensuring the correct FEC setting on the switch side according to the type of DAC you are using, you can resolve issues related to the link not getting online and ensure stable connectivity between your switch and storage.