Linux ethtool

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Linux ethtool

Use the ethtool command in Linux to display or change the settings of your Ethernet device. The device name is usually rendered as ethXwith X referencing the number of the device.

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The default Ethernet device is usually rendered as eth0. To change the settings for the specified Ethernet device, enter the command ethtool -s with the following switches:. Linux Switching from Windows. Tweet Share Email. Use the following switches to modify the command's function:.

This involves blinking one or more LEDs on the specific Ethernet port. N : The length of time to perform phys-id, in seconds. Offline performs a full set of tests and may cause normal operation interruption during the tests. Online performs a limited set of tests, and doesn't interrupt normal adapter operation. In the usual case it is, but might cause problems with some network devices, so you can turn it off.

Currently only internal and external can be specified, in the future further types might be added. Not all devices support this. The argument to this option is a string of characters specifying which options to enable. This option clears all previous options. The argument to this option must be 6 bytes in Ethernet MAC hex format xx : yy : zz : aa : bb : cc.

Meanings differ per driver. More from Lifewire.This family does not use a specific header, all information in requests and replies is passed using netlink attributes. The ethtool netlink interface uses extended ACK for error and warning reporting, userspace application developers are encouraged to make these messages available to user in a suitable way.

In some cases, the request as such is allowed for anyone but unprivileged users have attributes with sensitive information e. This implements an array of entries. Each request or reply message contains a nested attribute with common header. Structure of this header is. One of them is sufficient in requests, if both are used, they must identify the same device.

Some requests, e.

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Most GET requests also allow dump requests without device identification to query the same information for all devices providing it each device in a separate message. The interpretation of these flags is the same for all request types but the flags may not apply to requests. Recognized flags are:. New request flags should follow the general idea that if the flag is not set, the behaviour is backward compatible, i.

Monitoring Interfaces and Transceivers Using ethtool

A client must not set flags it does not understand. For arbitrary length bitmaps, ethtool netlink uses a nested attribute with contents of one of two forms: compact two binary bitmaps representing bit values and mask of affected bits and bit-by-bit list of bits identified by either index or name.

Verbose bit-by-bit bitsets allow sending symbolic names for bits together with their values which saves a round trip when the bitset is passed in a request or at least a second request when the bitset is in a reply. This is useful for one shot applications like traditional ethtool command.

On the other hand, long running applications like ethtool monitor displaying notifications or network management daemons may prefer fetching the names only once and using compact form to save message size. Notifications from ethtool netlink interface always use compact form for bitsets. In requests modifying a bitmap, the former changes the bit set in mask to values set in value and preserves the rest; the latter sets the bits set in the bitmap and clears the rest.

They consist of bit words in host byte order, words ordered from least significant to most significant i. Kernel bit set length may differ from userspace length if older application is used on newer kernel or vice versa. If userspace bitmap is longer, an error is issued only if the request actually tries to set values of some bits not recognized by kernel. Bit size is optional for bit-by-bit form.

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A bit may be identified by its index or by its name. A request fails if index exceeds kernel bit length or if name is not recognized.

Such bitset represents a bitmap with listed bits set and the rest zero. In requests, application can use either form. Semantics of value and mask depends on the attribute. GET requests are sent by userspace applications to retrieve device information.

They usually do not contain any message specific attributes. Only attributes where a change is requested are included in such request also, not all attributes may be changed. Data modification also triggers sending a NTF message with a notification. These usually bear only a subset of attributes which was affected by the change.

linux ethtool

The same notification is issued if the data is modified using other means mostly ioctl ethtool interface. Unlike notifications from ethtool netlink code which are only sent if something actually changed, notifications triggered by ioctl interface may be sent even if the request did not actually change any data.

ACT messages request kernel driver to perform a specific action. Performing an action also triggers a notification NTF message. There are two types of string sets: global independent of a device, e.Ethtool advertise options: speed and mode of operation. 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.

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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 see the man page, ethtool 8for a more comprehensive list and explanation.

The first two examples are information queries and show the use of the different formats of the command. For example eth0 or em1. 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:.

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

Here follows a list of command options to query, identify or reset the device. They are in the usual -short and --long form:. 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. The --show-time-stamping or -T option queries the specified network device for time stamping parameters.

The --show-featuresor --show-offloador -k option queries the specified network device for the state of protocol offload and other features. The --test or -t option is used to perform tests on a Network Interface Card.

Service will be interrupted.

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Service should not be interrupted. 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. It can be used in interface configuration files to set the desired options when the network interface is brought up.

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.

linux ethtool

Omitting the speed value will show the supported device speeds. The --duplex option is used to set the transmit and receive mode of operation. Usually used when connected to a hub. Usually used when connected to a switch or another host.

The --port option is used to select the device port. Normally used with hubs. 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.

linux ethtool

You can display the auto-negotiation state using the --a, --show-pause option.Time to be honest here for a minute. The open source community really has outdone themselves coming up with some very obscure names for packages.

Let's take this list of packages for instance: emacs, gimp, gcc, mutt, grub, kyle rankin, parted, tar, mutt, vim. Nine times out of ten, a common person is going to look at that list and become utterly confused over what package does what. That's just the beauty and beast of naming software in the open source community.

But every so often a tool comes across my screen with such a blatantly obvious name that I just have to run a 'man' to make sure my eyes are not deceiving me.

In this case, it's ethtool. Yes, a simple name, for such a powerful utility. The name itself tells you what it does, an Ethernet Tool. That's it, ethernet tool. What Ethtool does is allows you to modify your Ethernet adapter settings inside of Linux. What I'll be writing about today isn't the nitty gritty of ethernet adaptors coalesce, setting rings, register dumping, etc.

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But what I will address are some really nifty tips and tricks I have learned over the last decade or so. So without further adieu, let's get started. First things first we need to determine what Ethernet adaptor you are using. Keep in mind though, ethtool will only work against physical ethernet adapters.

This means that bond0, tun0, and any other network device that is not a physical network device will not work with ethtool. Now that you know your device, lets have some fun, shall we? Note: Most linux kernels mark ethernet devices as ethX, where X is the starting at 0 of the physical Ethernet interface.

I know I know, start with the least used things first. But hey, someone might find this useful, right? By running the following command you will get statistics about your network card. From here you can see a list of transmitted, received and errored packets. This can be useful during network troubleshooting, combined with other network utilities such as tcpdump.

I'm sure this has happened to many of you, as I know it has happened to me. Ever had a server with more than 2 network cards? Raise your hand. Ever had more than two? Ever had to trace what physical network card was recorded in linux as ethX? Sure, you could do it the hard way: grab the MAC address off of ifconfig, plug all the cables into a managed switch and then dump the tables on the switch to find what MAC address goes where.

Or, follow the blinking lights with ethtool. Look there! Blinking lights at the back of your ethernet adaptor. No need to hunt and peck to figure out what eth0 and eth1 is on your physical adaptor. Now, this is one that I haven't had to use before, as it's been a rare day that an Ethernet adapter has gone out on me. But nonetheless, this is still a useful switch to have in the sys admin's bag of tricks.It provides simple and fast way to get and set configuration about IP address, interface speed, interface duplex or half duplex etc.

We will start with simply listing given network interface properties. We will see that there is a lot of network interface properties which is outputted by ethtool.

ethtool: Linux Command/Unix Command

For this operation we do not need to provide any option. Network Interfaces are managed and used with drivers. Drivers are operating system level modules which is the same for network interface cards with same chipset.

As stated previously auto-negotiation is used to determine link speed of the network interface transmitter. The other end of the link is another factor for link speed.

We can enable auto-negotiation for talk the link speed with the remote host and set the best speed for the link. Network statistics provides useful information about network utilization of the system. We can change auto-negotiation of the given network interface card.

linux ethtool

We need root privileges becauase of system level chages. We can change the speed of the network interface card. This can be useful if remote interface do not supports auto-negotiation or there are link speed related problems.

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Also disabling auto-negotiation is good practice. As we know network interface cards have some leds to give information about traffic and link. We can blink these leds by using ethtool. This may be useful if we need to blink leds to specify network interface card. After a system reboot all configurations will be reset.

But we can make these configuration permanent in order to save configuration time. Just add following lines to the related operation system configuration file.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. Now GRO which is a linux network stack feature can be disabled using 'ethtool -k ethx gro off'.

Is that available for LRO as well? It should prevent the system from performing lro. However, many of the drivers which still use LRO are broken and do not honor ethtool. Learn more. Disabling LRO using ethtool? Ask Question. Asked 8 years, 10 months ago. Active 8 years, 10 months ago. Viewed 22k times. For readers: LRO stands for Large receive offload. And just fyi, there are issues with this in non linux protocol stacks too. As the checksum is not recalculated at least with gro this was the case certain network stacks like cisco's tcp will check the checksum and not be lenient like linux tcp is and ignore the error.

Active Oldest Votes. Yes, if your ethtool is new enough. Nemo Nemo Seth Robertson Seth Robertson 26k 4 4 gold badges 51 51 silver badges 49 49 bronze badges. This is wrong, -k lower case shows the settings. Nemo's answers is the proper usage. Sign up or log in Sign up using Google. Sign up using Facebook.

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