ethtool Fails to Force Duplex Mode



ethtool fails to force an interface into duplex mode.

root@switch:~# ethtool -s swp48 speed 100 duplex full autoneg off
Cannot set new settings: Operation not supported
not setting speed
not setting duplex
not setting autoneg

ethtool reports Cannot set new settings: Operation not supported.



  • Cumulus Linux 1.5.1 or earlier
  • cl-utilities version lower than 1.0-cl1.5.131120


Root Cause

The native Linux ethtool is not capable of configuring front panel ports.


Diagnostic Steps

  1. Attempt to configure a front panel port using ethtool. Observe the error Cannot set new settings: Operation not supported.
  2. Check the installed version of cl-utilities for a version earlier than 1.0-cl1.5.131120:

    root@switch:~# dpkg -l cl-utilities
    | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
    |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
    ||/ Name                    Version          Architecture     Description
    ii  cl-utilities            1.0-cl1.5.130925 powerpc          collection of cl commands



  1. Update cl-utilities to version 1.0-cl1.5.131120 (released with Cumulus Linux 1.5.2) or later. cl-utilities provides an ethtool wrapper to enable configuration of front panel ports.
  2. Set port mode to duplex using ethtool:

    root@switch:~# ethtool -s swp48 duplex full
  3. Check the port mode with ethtool:

    root@switch:~# ethtool swp8 |grep Duplex
    Duplex: Full
  4. The port on the opposite end of the link may need to be flapped in order for the change to take effect.

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