Commands to view Nexus FEC counters

[tim20110612]

Hi,

Can I view FEC corrected and incorrect codewords on a Cisco Nexus?

Similar to Arista's "show interfaces ethernet 2/1 phy detail" command.

Thank you!

[Jens Albrecht]

The commands and the information they provide depend on the platform, the NX-OS version and the transceiver type.

So we need to know the exact hardware and software to answer this question.

[tim20110612]

Hi Jens,

Thank you for your reply.

The hardware, software, and transceiver details we are currently using are as follows:

Hardware: cisco Nexus9000 C93600CD-GX
cisco Nexus9000 C93600CD-GX Chassis
Intel(R) Xeon(R) CPU D-1526 @ 1.80GHz with 32803120 kB of memory.
Processor Board ID FDO27440YVE
Device name: N9K-93600
bootflash: 115805708 kB

Software: NXOS version 10.5(1)
BIOS: version 05.51
NXOS: version 10.5(1) [Feature Release]
Host NXOS: version 10.5(1)
BIOS compile time: 11/29/2023
NXOS image file is: bootflash:///nxos64-cs.10.5.1.F.bin
NXOS compile time: 7/31/2024 12:00:00 [07/26/2024 02:00:41]
NXOS boot mode: LXC

Transceiver: 400G BASE LR4
N9K-93600# show interface ethernet 1/31 transceiver details
Ethernet1/31
transceiver is present
type is QSFP-DD-400G-LR4
name is Inphitech
part number is 7090004199
revision is 01
serial number is S251013GDXT00001
Nominal bitrate is 425000 MBit/sec per channel
cisco id is 24
cisco extended id number is 0
firmware version is 0.6
Link length SMF is 10 km
Nominal transmitter wavelength is 1310.00 nm
Wavelength tolerance is 6.500 nm
host count lane is 8
media count lane is 4
max module temperature is 70 deg C
min module temperature is 0 deg C
min operational voltage is 3.12 V
vendor OUI is 0x000000
date code is 251013
power class is 6 (12.0 W maximum)
max power is 12.00 W
near-end lanes used none
far-end lane code for 8 lanes Undefined
media interface is 1310 nm EML
Advertising code is Optical Interfaces: SMF
Host electrical interface code is 400GAUI-8 C2M (Annex 120E)
media interface advertising code is 400G-LR4

[Jens Albrecht]

Hi @tim20110612,

so check out the following 2 commands:

• show interface ethernet 1/31 phy detail
• show system internal ethpm info interface ethernet 1/31

The output of the second command is pretty lengthy but also contains the values for fec_corr_codewords and fec_uncorr_codewords.

HTH!

[Rockyw]

Yes, you can view FEC (Forward Error Correction) corrected and uncorrected codewords on Cisco Nexus switches, though the specific command and output details vary by platform and NX-OS release. Here's how to access this information:

1. Primary Command: show interface fec
·This command displays FEC-related statistics for interfaces, including corrected and uncorrected codeword counts on supported platforms (e.g., Nexus 9000 series with NX-OS Release 7.0(3)I7(7) or later).

·Example output (based on similar implementations):

Interface    Admin FEC    Oper FEC    Corrected Codewords    Uncorrected Codewords
Eth1/1       Auto         RS544       3,764,260,805          3,937,147,040

Note: The exact output fields (e.g., "Corrected Codewords" vs. "FEC Corrected Errors") depend on the hardware and software version.

2. Alternative Commands for FEC Data
·show interface transceiver performance-monitoring current fec:
Provides detailed FEC performance metrics, including error counts, on newer Nexus platforms (e.g., NX-OS 10.5(x)).
·show interface counters errors:
May include FEC-corrected error counters (e.g., fec-corrected) alongside other physical layer errors.
3. Platform and Release Considerations
·Nexus 9000: Full support for show interface fec starts with NX-OS 7.0(3)I7(7). Earlier releases may lack codeword-specific counters.
·Nexus 7000/3000: FEC support is limited to specific modules (e.g., M3 Gigabit Ethernet module on Nexus 7000)
, and commands may show only basic FEC status without detailed codeword counts.
·Nexus 9300-XF/GF: Requires explicit license enablement (e.g., NXOS_ESSENTIALS_XF) for advanced FEC features.
4. Comparison to Arista's Command
·While Arista's show interfaces ethernet 2/1 phy detail explicitly lists "FEC corrected codewords" and "FEC uncorrected codewords", Cisco's equivalent output is typically under show interface fec or transceiver PM commands.
·Cisco's output may use terms like "Corrected Errors" or "Uncorrected Words" instead of "codewords" in some contexts.
5. Verification and Troubleshooting
·Ensure FEC is enabled on the interface (e.g., via fec auto or fec rs544 configuration).
·If counters are absent, check platform support and NX-OS version compatibility.
·For real-time monitoring, use show interface fec periodically to track codeword error rates.
Summary
Use show interface fec on supported Nexus platforms (e.g., Nexus 9000 with NX-OS ≥7.0(3)I7(7)) to view corrected and uncorrected codeword counts. For older platforms or modules, check show interface counters errors or transceiver-specific commands. The output structure aligns with industry standards but may vary slightly from Arista's phrasing.