1.5. Ethtool

⁠1.5. Ethtool

Ethtool is a utility for configuration of Network Interface Cards (NICs). This utility allows querying and changing settings such as speed, port, auto-negotiation, PCI locations and checksum offload on many network devices, especially Ethernet devices.

We present here a short selection of often used ethtool commands together with some useful commands that are not well known. For a full list of commands type ethtool -h or refer to the man page, ethtool(8), for a more comprehensive list and explanation. The first two examples are information queries and show the use of the different formats of the command.

But first, the command structure:

ethtool [option...] devname

where option is none or more options, and devname is your Network Interface Card (NIC). For example eth0 or em1.

ethtool

The ethtool command with only a device name as an option is used to print the current settings of the specified device. It takes the following form:

ethtool devname

where devname is your NIC. For example eth0 or em1.

Some values can only be obtained when the command is run as root. Here is an example of the output when the command is run as root:

~]# ethtool em1
Settings for em1:
	Supported ports: [ TP ]
	Supported link modes:   10baseT/Half 10baseT/Full
	                        100baseT/Half 100baseT/Full
	                        1000baseT/Full
	Supported pause frame use: No
	Supports auto-negotiation: Yes
	Advertised link modes:  10baseT/Half 10baseT/Full
	                        100baseT/Half 100baseT/Full
	                        1000baseT/Full
	Advertised pause frame use: No
	Advertised auto-negotiation: Yes
	Speed: 1000Mb/s
	Duplex: Full
	Port: Twisted Pair
	PHYAD: 2
	Transceiver: internal
	Auto-negotiation: on
	MDI-X: on
	Supports Wake-on: pumbg
	Wake-on: g
	Current message level: 0x00000007 (7)
			       drv probe link
	Link detected: yes

Issue the following command, using the short or long form of the argument, to query the specified network device for associated driver information:

ethtool -i, --driver devname

where devname is your Network Interface Card (NIC). For example eth0 or em1.

Here is an example of the output:

~]$ ethtool -i em1
driver: e1000e
version: 2.0.0-k
firmware-version: 0.13-3
bus-info: 0000:00:19.0
supports-statistics: yes
supports-test: yes
supports-eeprom-access: yes
supports-register-dump: yes

Here follows a list of command options to query, identify or reset the device. They are in the usual -short and --long form:

--statistics

The --statistics or -S queries the specified network device for NIC and driver statistics. It takes the following form:

-S, --statistics devname

where devname is your NIC.

--identify

The --identify or -p option initiates adapter-specific action intended to enable an operator to easily identify the adapter by sight. Typically this involves blinking one or more LEDs on the specified network port. It takes the following form:

-p, --identify devname integer

where integer is length of time in seconds to perform the action,

and devname is your NIC.

--show-time-stamping

The --show-time-stamping or -T option queries the specified network device for time stamping parameters. It takes the following form:

-T, --show-time-stamping devname

where devname is your NIC.

--show-offload

The --show-features, or --show-offload, or -k option queries the specified network device for the state of protocol offload and other features. It takes the following form:

-k, --show-features, --show-offload devname

where devname is your NIC.

--test

The --test or -t option is used to perform tests on a Network Interface Card. It takes the following form:

-t, --test devname word

where word is one of the following:

offline — Perform a comprehensive set of tests. Service will be interrupted.
online — Perform a reduced set of tests. Service should not be interrupted.
external_lb — Perform full set of tests including loopback tests while fitted with a loopback cable.

and devname is your NIC.

Changing some or all settings of the specified network device requires the -s or --change option. All the following options are only applied if the -s or --change option is also specified. For the sake of clarity we will omit it here.

To make these settings permanent you can make use of the ETHTOOL_OPTS directive. It can be used in interface configuration files to set the desired options when the network interface is brought up. Refer to Section 1.2.1, “Ethernet Interfaces” for more details on how to use this directive.

--offload

The --features, or --offload, or -K option changes the offload parameters and other features of the specified network device. It takes the following form:

-K, --features, --offload devname feature boolean

where feature is a built-in or kernel supplied feature,

boolean is one of ON or OFF,

and devname is your NIC.

The ethtool(8) man page lists most features. As the feature set is dependent on the NIC driver, you should consult the driver documentation for features not listed in the man page.

--speed

The --speed option is used to set the speed in megabits per second (Mb/s). Omitting the speed value will show the supported device speeds. It takes the following form:

--speed number devname

where number is the speed in megabits per second (Mb/s),

and devname is your NIC.

--duplex

The --duplex option is used to set the transmit and receive mode of operation. It takes the following form:

 --duplex word devname

where word is one of the following:

half — Sets half-duplex mode. Usually used when connected to a hub.
full — Sets full-duplex mode. Usually used when connected to a switch or another host.

and devname is your NIC.

--port

The --port option is used to select the device port . It takes the following form:

--port value devname

where value is one of the following:

tp — An Ethernet interface using Twisted-Pair cable as the medium.
aui — Attachment Unit Interface (AUI). Normally used with hubs.
bnc — An Ethernet interface using BNC connectors and co-axial cable.
mii — An Ethernet interface using a Media Independent Interface (MII).
fibre — An Ethernet interface using Optical Fibre as the medium.

and devname is your NIC.

--autoneg

The --autoneg option is used to control auto-negotiation of network speed and mode of operation (full-duplex or half-duplex mode). If auto-negotiation is enabled you can initiate re-negotiation of network speeds and mode of operation by using the -r, --negotiate option. You can display the auto-negotiation state using the --a, --show-pause option.

It takes the following form:

--autoneg value devname

where value is one of the following:

yes — Allow auto-negotiating of network speed and mode of operation.
no — Do not allow auto-negotiating of network speed and mode of operation.

and devname is your NIC.

--advertise

The --advertise option is used to set what speeds and modes of operation (duplex mode) are advertised for auto-negotiation. The argument is one or more hexadecimal values from Table 1.1, “Ethtool advertise options: speed and mode of operation”.

It takes the following form:

--advertise option devname

where option is one or more of the hexadecimal values from the table below and devname is your NIC.

⁠

Table 1.1. Ethtool advertise options: speed and mode of operation

Hex Value	Speed	Duplex Mode	IEEE standard?
0x001	10	Half	Yes
0x002	10	Full	Yes
0x004	100	Half	Yes
0x008	100	Full	Yes
0x010	1000	Half	No
0x020	1000	Full	Yes
0x8000	2500	Full	Yes
0x1000	10000	Full	Yes
0x20000	20000MLD2	Full	No
0x20000	20000MLD2	Full	No
0x40000	20000KR2	Full	No

--phyad

The --phyad option is used to change the physical address. Often referred to as the MAC or hardware address but in this context referred to as the physical address.

It takes the following form:

--phyad physical_address devname

where physical_address is the physical address in hexadecimal format and devname is your NIC.

--xcvr

The --xcvr option is used to select the transceiver type. Currently only “internal” and “external” can be specified. In the future other types might be added.

It takes the following form:

--xcvr word devname

where word is one of the following:

internal — Use internal transceiver.
external — Use external transceiver.

and devname is your NIC.

--wol

The --wol option is used to set “Wake-on-LAN” options. Not all devices support this. The argument to this option is a string of characters specifying which options to enable.

It takes the following form:

--wol value devname

where value is one or more of the following:

p — Wake on PHY activity.
u — Wake on unicast messages.
m — Wake on multicast messages.
b — Wake on broadcast messages.
g — Wake-on-Lan; wake on receipt of a "magic packet".
s — Enable security function using password for Wake-on-Lan.
d — Disable Wake-on-Lan and clear all settings.

and devname is your NIC.

--sopass

The --sopass option is used to set the “SecureOn” password. The argument to this option must be 6 bytes in Ethernet MAC hexadecimal format (xx:yy:zz:aa:bb:cc).

It takes the following form:

--sopass xx:yy:zz:aa:bb:cc devname

where xx:yy:zz:aa:bb:cc is the password in the same format as a MAC address and devname is your NIC.

--msglvl

The --msglvl option is used to set the driver message-type flags by name or number. The precise meanings of these type flags differ between drivers.

It takes the following form:

--msglvl message_type devname

where message_type is one of:

message type name in plain text.
hexadecimal number indicating the message type.

and devname is your NIC.

The defined message type names and numbers are shown in the table below:

⁠

Table 1.2. Driver message type

Message Type	Hex Value	Description
drv	0x0001	General driver status
probe	0x0002	Hardware probing
link	0x0004	Link state
timer	0x0008	Periodic status check
ifdown	0x0010	Interface being brought down
ifup	0x0020	Interface being brought up
rx_err	0x0040	Receive error
tx_err	0x0080	Transmit error
intr	0x0200	Interrupt handling
tx_done	0x0400	Transmit completion
rx_status	0x0800	Receive completion
pktdata	0x1000	Packet contents
hw	0x2000	Hardware status
wol	0x4000	Wake-on-LAN status