Description

This issue occurs when the device fails to read diagnostic or operational data from the QSFP module via the I2C bus which may lead to the interface remaining down.

Symptoms

During this issue, the following symptoms may be observed:

  1. The interface may remain down.

  2. The interface may not come up immediately after applying a local loopback. It might take a few minutes to come up, only to go down again.

  3. The following log messages will be recorded:

fpc4 FXPC_QFX10_I2C_READ_FAILURE: qfx10_qsfp_i2c_read: PFE FPGA I2C Read failed bus_addr 50 group b bytes 1 starting_addr 5  

fpc4 FXPC_100G_QSFP_PORT_READ_FAILURE: qfx10_lc_100g_qsfp_read failed for port 21

fpc4 qsfp_tk_get_cdr_lol_state: qsfp-4/0/21 failed to read CDR LOL regerr 1000 

fpc4 qsfp-4/0/21 set to not present 

fpc4 qsfp-4/0/21 plugged in 

 

Solution

These messages indicate that the device failed to read data from the QSFP module using the I2C (Inter-Integrated Circuit) bus.

The I2C bus is used to communicate between the control plane and the QSFP transceiver module to read diagnostic information, monitor status, etc.

PFE FPGA I2C Read failed, so the request to read from the I2C bus to the QSFP module was unsuccessful.

To troubleshoot and resolve this issue, perform the following steps:

1) Check the Rx/Tx Status:

Use the following command to check the optical diagnostics of the interface:

show interfaces diagnostics optics interface-name


2) Reseat the QSFP Module:
Physically remove and reinsert the QSFP module into the affected port.

3) Test with a Working Link:
Connect a known working link to the problematic interface and check if the issue persists. If the issue remains, proceed to the next step.

4) Move the Link and QSFP to Another Port:
Connect the impacted link and QSFP to a different port. If the interface comes up, continue with the following steps.

5) Apply a Local Loopback:

Apply a local loopback to the interface:

set interfaces interface-name (fastether-options | gigether-options) loopback


6) Check the Interface Status:
If the interface doesn’t come up immediately after applying the loopback and takes 3-4 minutes to stabilize, move to the next step.

 

7) Restart the PIC:

Restart the Physical Interface Card (PIC) associated with the interface:

request chassis pic offline fpc-slot slot-number pic-slot slot-number

8) Check if any error log messages are present for respective FPC and restart it.

If the issue persists, restart FPC:

request chassis fpc slot slot-number restart

If issue persist then please reach out to Juniper technical support representative for further investigation.

Modification History

2024-10-08 : Article Created