Intermittent SFP - uplink flapping under high utilization

Question

Intermittent SFP - uplink flapping under high utilization

Sahil Soni 100

Hi guys

We have an SFP+ uplink between our distribution switches that intermittently flaps whenever link utilization becomes high.

I'd like to verify whether the issue could be related to the optical signal levels. Could you please advise how to check and measure the optical receive power (Rx) levels directly from the CLI ? If there are any recommended commands or additional transceiver diagnostics that should be reviewed while troubleshooting this type of issue, I would appreciate your guidance.

Thank you.

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Answer 1

Hi Sahil Soni,

To measure optical receive power (Rx) and Digital Optical Monitoring (DOM) metrics from the CLI, run the command matching your switch platform: show interfaces TenGigabitEthernet1/0/1 transceiver detail on Cisco IOS/IOS-XE (enabling polling globally with transceiver type all followed by monitoring if disabled on older platforms), show interface Ethernet1/1 transceiver details on Cisco NX-OS, show interfaces Ethernet1 transceiver dom on Arista EOS, show interfaces diagnostics optics xe-0/0/0 on Juniper Junos, or show interface 1/1/1 transceiver detail on HPE Aruba AOS-CX.

In the command output, evaluate the Optical Receive Power (Rx Power) in decibel-milliwatts (dBm), where values closer to zero represent a stronger signal. Typical healthy ranges sit around -1.5 dBm to -9.0 dBm for 10GBASE-SR multimode optics and -1.0 dBm to -12.0 dBm for 10GBASE-LR single-mode optics, but you should always compare your live reading directly against the transceiver's factory-calibrated Low Warning and Low Alarm threshold columns displayed in the table. Compare local Rx Power against the remote switch's Transmit Power (Tx Power) to measure fiber attenuation, and ensure Rx Power stays at least 1.5 dB above the low-warning threshold. In the same table, verify that internal module temperature stays safely below the 70 degrees Celsius commercial limit during heavy chassis load, and confirm that Laser Bias Current (mA) is not climbing toward its high-warning threshold while Tx Power drops, which indicates a degrading laser diode.

Hope this answer has brought you some useful information. If it did, please hit “accept answer”. Should you have any questions, feel free to leave a comment.

VPHAN