Useful ethtool commands

Ethtool is a user space utility for displaying and configuring the Network Interface Unit. This article is an attempt to summarise the most useful ethtool commands with examples

Ethtool for ethtool

Ethool provides commands like ethtool -h which contains a pretty good documentation of the tool usage.

man ethtool gives further information about how to use ethtool

ethtool -version : the current version of ethool

Installation

apt-get install ethtool

Ethool Query Commands

To check the current settings of the nic interface.

ethool ethX

Settings for eno1:
 Supported ports: [ TP ]
 Supported link modes: 10baseT/Half 10baseT/Full 
 100baseT/Half 100baseT/Full 
 1000baseT/Half 1000baseT/Full 
 Supported pause frame use: No
 Supports auto-negotiation: Yes
 Supported FEC modes: Not reported
 Advertised link modes: 10baseT/Half 10baseT/Full 
 100baseT/Half 100baseT/Full 
 1000baseT/Half 1000baseT/Full 
 Advertised pause frame use: Symmetric
 Advertised auto-negotiation: Yes
 Advertised FEC modes: Not reported
 Link partner advertised link modes: 10baseT/Half 10baseT/Full 
 100baseT/Half 100baseT/Full 
 Link partner advertised pause frame use: Symmetric
 Link partner advertised auto-negotiation: Yes
 Link partner advertised FEC modes: Not reported
 Speed: 100Mb/s
 Duplex: Full
 Port: Twisted Pair
 PHYAD: 1
 Transceiver: internal
 Auto-negotiation: on
 MDI-X: on
Cannot get wake-on-lan settings: Operation not permitted
 Current message level: 0x000000ff (255)
 drv probe link timer ifdown ifup rx_err tx_err
 Link detected: yes

• Speed: The speed in which the interface is configured
• Duplex: The duplex mode device is configured
• Link detected : Shows if the physical interface is actually connected to the network
• Information about the Supported speeds and Duplex modes
• Idea about whether the interface supports auto negotiation or not or forward error correction is supported or not

All the information can be useful links to the current state of the interface.

ethtool -i ethX

driver: tg3
version: 3.137
firmware-version: FFV20.6.18 bc 5720-v1.39
expansion-rom-version: 
bus-info: 0000:04:00.0
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes
supports-priv-flags: no

Giving out the more driver specific information of the interface

• The driver and the version of the driver is available from here.
• The Bus information which is available in lspci
• The “supports” prefix parameters gives insight about the other supported commands in the ethtool by the driver.

Ethtool Debug Command

This category of commands can be used for debugging purpose.

ethtool -S ethX

NIC statistics:
 rx_packets: 0
 tx_packets: 0
 rx_bytes: 0
 tx_bytes: 0
 rx_broadcast: 0
 tx_broadcast: 0
 rx_multicast: 0
 tx_multicast: 0
 rx_errors: 0
 tx_errors: 0
 tx_dropped: 0
 multicast: 0
 collisions: 0
 rx_length_errors: 0
 rx_over_errors: 0
 rx_crc_errors: 0
 rx_frame_errors: 0
 rx_no_buffer_count: 0
 rx_missed_errors: 0
 tx_aborted_errors: 0
 tx_carrier_errors: 0
 tx_fifo_errors: 0
 tx_heartbeat_errors: 0
 tx_window_errors: 0
 tx_abort_late_coll: 0
 tx_deferred_ok: 0
 tx_single_coll_ok: 0
 tx_multi_coll_ok: 0
 tx_timeout_count: 0
 tx_restart_queue: 0
 rx_long_length_errors: 0
 rx_short_length_errors: 0
 rx_align_errors: 0
 tx_tcp_seg_good: 0
 tx_tcp_seg_failed: 0
 rx_flow_control_xon: 0
 rx_flow_control_xoff: 0
 tx_flow_control_xon: 0
 tx_flow_control_xoff: 0
 rx_csum_offload_good: 0
 rx_csum_offload_errors: 0
 rx_header_split: 0
 alloc_rx_buff_failed: 0

Above command can be used to extract the network usage statistics. Different drivers support different parameters but the mainly supported once are the tx/rx packet statistics

ethtool -m ethX

Identifier : 0x11 (QSFP28)
 Extended identifier : 0x00
 Extended identifier description : 1.5W max. Power consumption
 Extended identifier description : No CDR in TX, No CDR in RX
 Extended identifier description : High Power Class (> 3.5 W) not enabled
 Connector : 0x23 (No separable connector)
 Transceiver codes : 0x88 0x00 0x00 0x00 0x00 0x00 0x00 0x00
 Transceiver type : 40G Ethernet: 40G Base-CR4
 Transceiver type : 100G Ethernet: 100G Base-CR4 or 25G Base-CR CA-L
 Encoding : 0x05 (64B/66B)
 BR, Nominal : 25500Mbps
 Rate identifier : 0x00
 Length (SMF,km) : 0km
 Length (OM3 50um) : 0m
 Length (OM2 50um) : 0m
 Length (OM1 62.5um) : 0m
 Length (Copper or Active cable) : 2m
 Transmitter technology : 0xa0 (Copper cable unequalized)
 Attenuation at 2.5GHz : 5db
 Attenuation at 5.0GHz : 7db
 Attenuation at 7.0GHz : 9db
 Attenuation at 12.9GHz : 14db
 Vendor name : Mellanox
 Vendor OUI : 00:02:c9
 Vendor PN : MCP1600-C002
 Vendor rev : A3
 Vendor SN : MT1845VS01580
 Date code : 181028
 Revision Compliance : SFF-8636 Rev 2.0
 Module temperature : 0.00 degrees C / 32.00 degrees F
 Module voltage : 0.0000 V

Gives out the transceiver specific information. The current temperature and voltage can be of particular interest in this case.

Ethtool Control commands

Can be used to control the configuration of the interface.

Physical interface setting

ethtool -s ethX speed 1000 duplex full autoneg on

Allows to configure the interface speed to (1000) duplex mode to (full) and auto negotiation (enabled)

This would be accepted only if it is listed on supported/advertised modes and the combination should be supported by ethtool

ethtool -s ethX advertise

Limits helps advertise a subset of the advertised modes. It takes hex arguments and below is the accepted inputs.

                  0x001                  10baseT Half
                  0x002                  10baseT Full
                  0x004                  100baseT Half
                  0x008                  100baseT Full
                  0x80000000000000000    100baseT1 Full
                  0x010                  1000baseT Half               (not supported by IEEE standards)
                  0x020                  1000baseT Full
                  0x100000000000000000   1000baseT1 Full
                  0x20000                1000baseKX Full
                  0x20000000000          1000baseX Full
                  0x800000000000         2500baseT Full
                  0x8000                 2500baseX Full               (not supported by IEEE standards)
                  0x1000000000000        5000baseT Full
                  0x1000                 10000baseT Full
                  0x40000                10000baseKX4 Full
                  0x80000                10000baseKR Full
                  0x100000               10000baseR_FEC
                  0x40000000000          10000baseCR  Full
                  0x80000000000          10000baseSR  Full
                  0x100000000000         10000baseLR  Full
                  0x200000000000         10000baseLRM Full
                  0x400000000000         10000baseER  Full
                  0x200000               20000baseMLD2 Full           (not supported by IEEE standards)
                  0x400000               20000baseKR2 Full            (not supported by IEEE standards)
                  0x80000000             25000baseCR Full
                  0x100000000            25000baseKR Full
                  0x200000000            25000baseSR Full
                  0x800000               40000baseKR4 Full
                  0x1000000              40000baseCR4 Full
                  0x2000000              40000baseSR4 Full
                  0x4000000              40000baseLR4 Full
                  0x400000000            50000baseCR2 Full
                  0x800000000            50000baseKR2 Full
                  0x10000000000          50000baseSR2 Full
                  0x10000000000000       50000baseKR Full
                  0x20000000000000       50000baseSR Full
                  0x40000000000000       50000baseCR Full
                  0x80000000000000       50000baseLR_ER_FR Full
                  0x100000000000000      50000baseDR Full
                  0x8000000              56000baseKR4 Full
                  0x10000000             56000baseCR4 Full
                  0x20000000             56000baseSR4 Full
                  0x40000000             56000baseLR4 Full
                  0x1000000000           100000baseKR4 Full
                  0x2000000000           100000baseSR4 Full
                  0x4000000000           100000baseCR4 Full
                  0x8000000000           100000baseLR4_ER4 Full
                  0x200000000000000      100000baseKR2 Full
                  0x400000000000000      100000baseSR2 Full
                  0x800000000000000      100000baseCR2 Full
                  0x1000000000000000   100000baseLR2_ER2_FR2 Full
                  0x2000000000000000     100000baseDR2 Full
                  0x4000000000000000     200000baseKR4 Full
                  0x8000000000000000     200000baseSR4 Full
                  0x10000000000000000  200000baseLR4_ER4_FR4 Full
                  0x20000000000000000    200000baseDR4 Full
                  0x40000000000000000    200000baseCR4 Fullethtool  — setfec ethX baser

To set the forward error correction mode.

ethtool – set-fec eth<x> encoding auto|off|rs|baser

The supported mode and the current setting can is displayed on

ethtool – show-fec eth<x>

ethtool — set-priv-flags

sets or resets the private flags specific to the device. Useful when you want to have a specific configuration for your driver.

Tuning and/or configuring the device

Display the default rx/tx queue size

ethtool -g ethX
Ring parameters for eth2:
Pre-set maximums:
RX:             1048576
RX Mini:        0
RX Jumbo:       0
TX:             1048576
Current hardware settings:
RX:             1024
RX Mini:        0
RX Jumbo:       0
TX:             4096

Modify the default rx/tx queue size using

ethtool -G eth2 rx 4096 tx 4096

Debug Configurations

ethtool -K ethX rx-all on

Forwarding ingress error packets to network stack

Useful when error packets has to be forwarded to network stack for analysis (eg. tcpdump). Driver by default drops ingress packets received with errors

ethtool -s ethX msglvl 0x40 << Displays Rx packet error levels and codes setup by HW
ethtool -s ethX msglvl 0x80 << Packet transmission errors

Enables the driver debug prints.

Ethtool provides many other options not explained above. There is a good documentation at http://man7.org/linux/man-pages/man8/ethtool.8.html