Configuring FEC on Optic Modules

This chapter provides information on how to configure FEC on optica modules.

Feature History for FEC Support on Optic Modules

This table includes only the updates for those releases that have resulted in additions or changes to the feature.

Table 1. Feature History for FEC Support on Optic Modules

Feature Name

Release

Feature Information

FEC Support on Optic Modules

8.0(1)

Added support for the FEC Support on Optic Modules feature on the Cisco Nexus 7000 Series Switches M3 100 Gigabit Ethernet module (N77-M312CQ-26L).

Information About FEC Support on Optic Modules

From Cisco NX-OS Release 8.0(1), Forward Error Correction (FEC) support is enabled on the Cisco Nexus 7000 Series Switches M3 Gigabit Ethernet module (N77-M312CQ-26L).

FEC is a digital signal processing technique used to enhance data reliability. It is done by introducing redundant data, called error correcting code, prior to data transmission or storage.

FEC State Links

The following table list the expected link state when two devices are configured with different operational FEC configuration values. The following values are applicable only for QSFP-100G-SR4 transceiver modules.

Device 1 (Admin State)

Device 2 (Admin State)

Link State

FEC AUTO

FEC OFF

Down

FEC AUTO

FEC AUTO

UP

FEC OFF

FEC OFF

UP

FEC cl91

FEC AUTO

UP

FEC AUTO

FEC AUTO

UP

FEC cl91

FEC cl91

UP


Note

By default, the FEC admin state is AUTO. Operational state for all optics except QSFP-100G-LR4 transceiver modules will be negotiated to cl91 (ON). For QSFP, by default, the FEC operational state will negotiate to OFF. In a FEC set up, if one side of the link is set to AUTO and the other side of the FEC link is set to OFF, it can cause link failure (link down).

Configuring FEC on a Transceiver Module

Procedure

Step 1

Enter global configuration mode.

switch# configure terminal

Step 2

Specify an interface range to configure, and enter interface configuration mode.

switch(config)# interface interface-range

Step 3

Configure the Forward Error Correction feature for the interface range.

switch(config-if-range)# fec {auto | cl91 | off}

  • auto—Enables the FEC feature based on the transceiver type.

  • cl91—Enables clause 91 for 100 Gigabit interface.

  • off—Disables FEC for the interface range.

Note

 

The default admin mode is auto on all transceiver modules, but on the QSFP-100G-LR4 transceiver module by default, the admin mode is auto and the operational state of FEC is OFF.

Step 4

(Optional) Copy the running configuration as startup configuration.

switch(config)# copy running-config startup-config

Step 5

(Optional) Verify the FEC configurations.

switch(config)# show interface interface-range status

Configuring FEC

This example shows how to configure and verify the FEC feature on a QSFP-100G-LR4 transceiver module:

switch# configure terminal
switch(config)# interface ethernet1/2,Ethernet 18/12
switch(config-if-range)# fec cl91
switch(config-if-range)# exit
switch(config)# copy running-config startup-config
switch(config)# exit
switch#  show interface Ethernet1/2

Ethernet1/2 is up
admin state is up, Dedicated Interface
  Hardware: 40000/100000 Ethernet, address: 00eb.d56e.9fd0 (bia 00eb.d56e.9fd0)
  MTU 9216 bytes, BW 40000000 Kbit, DLY 10 usec
  reliability 255/255, txload 1/255, rxload 1/255
  Encapsulation ARPA, medium is broadcast
  Port mode is access
  full-duplex, 40 Gb/s, media type is 40G
  Beacon is turned off
  Auto-Negotiation is turned on
  Input flow-control is off, output flow-control is off
  Auto-mdix is turned off
  Rate mode is dedicated
  Switchport monitor is off
  EtherType is 0x8100
  EEE (efficient-ethernet) : n/a
    admin fec state is auto, oper fec state is off
  .
  .
  .