Technical Tip: Port speed configuration for DAC (Direct Attach Copper) cable

Description

This article describes the Port speed configuration recommended when using DAC cable.

Scope

FortiSwitch-448 series and above.

Solution

By default the speed config set on the SFP port is auto-module:

config switch physical-port
    edit "port52"
        set lldp-profile "default-auto-isl"
        set speed auto-module
    next
end

While using DAC cable for example: 10gbps, consider changing the speed to 10000cr.

config switch physical-port
    edit port52
        set speed 10000cr
end

To push the speed configuration from FortiGate for managed FortiSwitches, run the below command on FortiGate:

FGT# config switch-controller managed-switch

FGT(managed-switch) # edit <SWITCH-ID>

FGT(SWITCH-ID) # config ports

FGT(ports) # edit port#

FGT(port#) # set speed 10000cr

FGT(port#) # end

FGT(SWITCH-ID) # end

Reason:

It is recommended to change the speed configuration for the DAC cable to avoid CRC alignment errors and Rx errors.