Can't Configure 10G or 40G Port for 10/100M Speed

Issue

I am unable to set a 10G or 40G port to 10/100M speed. I am unable to establish a link between a 10G or 40G port and a 10/100M Ethernet segment.

Environment

Cumulus Linux, all versions

Solution

Use an intervening 1G switch to connect to the slower Ethernet segment.  The following configuration, for example, can be used to set a 10G port to 1G:

auto swp1
iface swp1 
    link-speed 1000 
    link-duplex full 
    link-autoneg off

For more information on configuring port speeds, see the Cumulus Linux User Guide:

• Cumulus Linux user guide - Configuring Switch Port Attributes

Root Cause

Speed reduction from 10G or 40G to 10/100M is unsupported at the hardware layer.