Link detected no in ethtool. Preferably using BASH scripting only.

Link detected no in ethtool. The ethtool command shows Link detected: no for interface The ip link command shows UP but NO CARRIER The mii-tool command shows SIOCGMIIPHY on 'ethX' failed The network link light is on but the interface will not come up The message ADDRCONF(NETDEV_UP): ethX: link is not rea On a Red Hat VM, if I disconnect the NIC, ethtool immediately shows Link detected: no instead of Link detected: yes, and ip link show shows <NO-CARRIER,BROADCAST,MULTICAST,UP> The ethtool command shows Link detected: no for interface The ip link command shows UP but NO CARRIER The mii-tool command shows SIOCGMIIPHY on drv probe link Link detected: no There is no cable connected in eth3, but ethtool output looks almost the same: diff <(ethtool eth2) <(ethtool eth3) 1c1 < Settings for eth2: --- > Settings for I have a linux firewall which has a network card, eth1 that insists the link is down, despite having a link light on the card itself. No link is getting ready: Link detected: no (Power budget exceeded) After that I asked google for help. The following solutions which have 以下のコマンドで確認できます。 ethtool eth0 | grep "Link detected" Link detected: yes であれば、物理的に接続されていることを意味リンクダウン（断線している）状態です。 Link detected: no 以上、ネットワークのリンク速度やケーブル断線を検出するコマンド ethtool の紹介でした。参考＠IT：ネットワークインターフェイスの状況を調べるには ethtool 请考虑以下示例： ethtool eth0 | grep Link\ d Link detected: yes ip link set dev eth0 down ethtool eth0 | grep Link\ d Link detected: no 结束语在本指南中，我 On a SLES12 with 4 physical NIC, having them in a bond0. ethernet supports-statistics: yes supports-test: no supports-eeprom-access: no supports-register-dump: yes supports-priv-flags: no Basically all of my statistics CentOS网卡无法联网，ethtool显示Link detected: no Speed: Unknown! Duplex: Unknown! (255)是设置错误造成的，解决方法为： 1、编辑虚拟机。 2、点击添加。 3、点击网络适配器，并点击完成。 4、新的网卡选择NAT模式，并点击确定。 5、点击开启虚拟机。 6、记住UUID，把其它网卡配置文件拷贝一份然后替换新的UUID Say that we have the wireless interface wlan0. Discover essential options, examples, and advanced This above ethtool output displays ethernet card properties such as speed, wake on, duplex and the link detection status. You can see Link detected: no or state DOWN in both the commands above. After I updated it to the latest firmware, "Link detected" is stable. The following outputs are produced: NICの状態を表示する。 # ethtool eth0 通常のサーバで実行すると以下のように表示される。 Settings for eth0: Supported ports: [ TP ] Supported link modes: Ethtool utility is used to view and change the ethernet device parameters. With copper, 'ethtool ens802s0f0' will tell you "Link detected: yes" or "Link detected: no. This command displays the settings of I also tried to enforce those settings on the Mellanox card with ethtool: $ ethtool -s enp38s0f0np0 speed 25000 autoneg off duplex full But that didn’t make a difference, so I turned autonegotiation back on. If you unplug that one it should go to "link detected: no". 简单介绍ethtool工具的几种用法1. ) Current setup: bond0 using eth0 and eth2 <-- bond0 working no issues bond0 is up with eth0, but for eth2 says no link detected. Changes to network speed, duplex On a OpenStack VM I see only # ethtool eth0 Settings for eth0: Link detected: yes On RHEV VM the same small output. I am using DAC-QSFP-100G 1M cable. Also lspci -k so we can see which kernel module your NIC uses. Preferably using BASH scripting only. When you execute ethtool command with a device name, it 检查输出中的 Link detected 字段：如果显示 Link detected: yes，表示网线已插入。如果显示 Link detected: no，表示网线未插入或连接异常。 Since I ran some update in the past week or so, I have not been able to get a wired connection. here is my setup up using ubuntu 8. /sbin/ethtool "$1" | grep -q "Link detected: yes" } if check_eth eth0; then echo "Online" else echo "Not online" fi How it works: if simply interprets a Link detected: no I've tried also sudo ethtool -p enp3s0 15 and got the following output (irrespectively of the cable being plugged in or not): Cannot identify NIC: Operation not supported The output of dmesg -t --level=alert,crit,err,warn is: NVRM: This PCI I/O region assigned to your NVIDIA device is invalid: NVRM: BAR0 is 0M @ 0x0 【摘要】 Ethtool 实用程序用于查看和更改以太网设备参数。1. Now after connecting the physical link to the network port , on re-executing the command status is displayed as below # ethtool eno1 Settings for eno1: Supported ports: [ TP ] No network connectivity and ethtool reports link speed and duplex as unknown: # ethtool eth0 Settings for eth0: Supported ports: [ FIBRE ] Supported link modes: 1000baseT/Full 文章浏览阅读9. 1. 04lts, 32bit server Dell 2650 Server with 3 nics, all gig ports ethtool -i eth0 (GB1 Could it be that the: ethtool ethx | grep detected shows "no link detected" if the bond0 isn't configured yet on OS (linux) side? isn't ethtool showing a physical state? I have an interesting issue. Take a look at the methods below to see how. g. I can This was working fine until a while back were both servers lost connection over fibre. I found the following both commands: mixconfig -e -d Link detected: no Driver details root@xilinx:~# ethtool -i eth0 driver: macb version: 5. Following are the three types of duplexes available. Looking in ethtool I get the details for the connection with link CentOS网卡无法联网，ethtool显示Link detected: no Speed: Unknown! Duplex: Unknown! (255)是设置错误造成的，解决方法为： 1、编辑虚拟机。 2、点击添加。 3、点击网络适配器，并点击完成。 4、新的网卡选择NAT模式，并点击确定。 5、点击开启虚拟机。 6、记住UUID，把其它网卡配置文件拷贝一份然后替换新的UUID和 If a network interface card (NIC) is causing problems on your Ubuntu Server, see how to use the ethtool command to troubleshoot the issue. Having trouble lately with a network interface that goes hang or suddenly "Link detected: no" when huge/spike network traffic happens and only fixed if the server restarted. However, many of the fields in ethtool, like Supported Link Modes and Advertised Link Modes are not updated based on the actual module inserted in the port and therefore are incorrect or ethtool eth0 | grep detect （检测到没有载波） Link detected: no 连接检测为no NOW pull on the wire plug mii-tool -w eth0 （跟踪物理链路并且激活状态灯，可以看到连接是否在线） 16:31:12 eth0: no link （发现没有连接） 16:31:20 eth0: drv probe link Link detected: no Notice from above highlighted display , "Link detected" has a value "no" which indicates the physical link is down . Let’s start by testing our eth0 network interface for a physica Hi all, When I run ethtool against ethernet card, I get following output - [***@datablade1 ~]# ethtool eth3 Settings for eth3: Supported ports: [ FIBRE ] Supported link modes: There seems to be no way to disable Green Ethernet in the config menu of the router, though. Can’t install the mft pcap. I have a HS20 blade, and I use bonding to do the failover. eth0 shows "Link detected: no". The output of ethtool is exactly the same as if no network cable was plugged in: root@shuttle:~# ethtool p33p1 Settings for p33p1: Supported ports: [ TP MII ] Supported link modes: 10baseT/Half 10baseT/Full Hi, I have two Intel i7-10700K PC, and two Intel E810-C for QFP (rev 02) Ethernet Controllers. However when I ran the following command: # ethtool wlp5s0 Output: Link Detected: yes I am use Port: Twisted Pair PHYAD: 1 Transceiver: internal Auto-negotiation: off Supports Wake-on: puag Wake-on: g Link detected: no ←接続されていない事を示している上記の様に、最後の行で no と表示されていたら、ネットワークに接続されていないという事になります。ネットワークの速 Hello, I built a server with 3x Mellanox Connectx4. " This is not true of SFP+ interfaces, at least in the farm I support. What does ip link set wlan0 up/down actually do? Power and poweroff the NIC? A lot of network configuration guides online nonchalantly describe it as simply "bringing the interface up", but what does that really mean? Linux如何检查网口是否插了网线如何使用Bash命令和Ethtool检测物理网络电缆连接检测是否连接了物理网线测试“eth0”网络接口的物理电缆连接： # cat /sys/class/net/eth0/carrier 1 数字1表示网线已经连接到网卡的插槽。 # ethtool eth0 → Link detected: no #/sbin/ifconfig eth0 up → インターフェースは起動しない LANケーブルを接続しているのに「Link detected: no」ということなので、ネットワークはハード的に動作しないということでしょうか。 Ether周辺のカスタマイズは行っていません。单片机连接电脑时出现“No ST-LINK Detected”的解决方案当单片机通过ST-LINK调试工具连接到电脑时，如果提示“No ST-LINK Detected”，通常是由于驱动问题、固件版本不匹配或物理连接异常等原因造成的。以下是详细的分析与解决方法： 1. 文章浏览阅读4. 2 firmware-version: expansion-rom-version: bus-info: ff0e0000. 安装ethtool工具Ethtool是用于查询及设置网卡参数的命令。这个工具没有预装在Ubuntu中，需要单独安装。安装方式： sudo apt-get i Oracle Linux: "ethtool" Command Shows "Link detected: no" for a Particular Network Interface (Doc ID 2513532. Does anyone have an idea how I could fix this problem? I tried to manually tell the network "No link detected" from ethtool and mii-tool Solution In Progress - Updated August 5 2024 at 6:45 AM - English My ethernet connection works fine in windows 8. Once I put in my QSFP28 LR-4 Optic and patch it, I can read the following if running ethtool. But when I connected only one of the ports, both interface shows link detected $ ethtool enp24s0f0 Settings for enp24s0f0: Cannot get wake-on Supports Wake-on: d Wake-on: d Current message level: 0x00000007 (7) drv probe link Link detected: yes 3. For me " Link detected: no " confirm this hypothesis. Learn how to use ethtool to diagnose and Switch side: Interface is up in individual mode (since no LACPDUs are received) Server side: No link detected Transceiver is detected! It's a DAC cable so 6. Or do I need configure the switch? The 10gbps is work just fine. From the output, In a Linux environment, I need to detect the physical connected or disconnected state of an RJ45 connector to its socket. sudo ethtool enp1s0 Settings for enp1s0: Supported ports: [ ] Supported link modes: 25000baseCR/Full 25000baseSR/Full 50000baseCR2/Full 100000baseSR4/Full 100000baseC As discussed in the comments and based on the test (unsuccessful) to bring up interface with command: ethtool -s enp0s31f6 speed 100 duplex full I will say you have broken ethernet adapter. 04 it does not detect the link Here's the output of ethtool eth0: Settings for eth0: Supported ports: [ TP MII ] Supported link What 'ethtool' reports mostly depends on what the network device driver can provide. is not configured with IP. 2k次，点赞4次，收藏5次。本文提供了一套全面的指南，帮助用户解决Ubuntu系统下无法上网的问题。涵盖了网络配置检查、网卡驱动确认、手动配置IP地址等多种实用技巧。 When I plug the network cable in, the Shuttle does not detect the connection and can thus not communicate with the network. Also you can consider to send the machine in service center You simply need if /sbin/ethtool eth0 | grep -q "Link detected: yes"; then echo "Online" else echo "Not online" fi Also if you want to encapsulate checking, simply use a function: function check_eth { set -o pipefail # optional. Please post output of ip addr show and (as root) output of ethtool your-interface . e. I've got an OpenWRT-based computing cluster named Mixtile Cluster Box using an ethernet port for connection to the outside world. E. 10. I wish to see something like (the spee ethtool は、Linux 上のネットワークユーティリティです。 Linux 上でイーサネットデバイスを構成するために使用されます。 ethtool を使用すると In Linux, is there any difference between after- ip link down -condition and real link absence (e. But if I remove eth0 from the bond0 and do an "ifup eth0", it will show "Link detected: yes" and everyth How To:Linux下如何通过命令检查网卡是否插上网线主要工具为ethtool来检查，主要关注的字段为"Link detected"，注意如下的输出，其中em4实际物理上并未插上网线，而em1是插上网线的： # ethtool em4 Settings for em4: S Link detected: no If there is a need to configure a TCP/IP address without connecting to the network, please add the following settings to each Ethtool in Linux that helps in troubleshoot Network Interface related problems and how to resolve the same. i changed the Try doing "ethtool enp2s0" and look at the "link detected: yes". 04lts, 32bit server Dell 2650 Server with 3 nics, all gig ports ethtool -i eth0 (GB1 My ethernet connection works fine in windows 8. I just want to connect 40gpbs. 列出以太网设备属性当您使用设备名称执行 ethtool 命令时，它会显示有关以太网设备的以下信息。# ethtool eth0Settings for eth0: Supported ports: [ TP ] Supported link modes: 10baseT/Half 10baseT/Fu 0. By difference I mean some signs in the system that can be used to distinguish these two conditions. But in ubuntu 15. I have used Various tools can be used to detected a physical cable carrier state. However, the easiest accomplish this task is by using basic native tools like cat or grepthus to avoid any need for additional software installation. 1) Last updated on MARCH 28, 2025 Applies to: Linux OS - Version Oracle Linux 5. Also, now ethtool doesn't seem to accept multiple config settings in one cmd line anymore, which used to work just fine: 新硬件单板回来，ping不通是一个常见问题，最近刚好碰到一个。两个 GE网口通过背板直连，网口都已识别，但是ping不通对端，排查步骤 1、查看检测网口是否link ethtool eth0 Link detected: no 2、关闭网口自协商模式 ethtool -s eth0 autoneg off speed 1000 duplex full 3、查看网口是否link ethtool eth0 Link detected: yes 4、A ethtoolコマンドの Link detected: の欄を見るとそもそもネットに繋がる環境かどうかがわかるつながるとき Link detected: yesになっている The switchd process keeps the hardware and kernel in sync for the important port settings (speed, auto-negotiation, and link detected) when they change. 8w次，点赞5次，收藏38次。本文详细介绍ethtool工具的功能，包括显示和设置网卡的基本属性、协商模式、收发包统计等。并提供实际操作示例，演示如何通过ethtool调整网络设备的速度、双工模式以及自动协商状态。 Link detected: no root@magiatiko:[~]#ethtool -s eth1 autoneg on root@magiatiko:[~]#ethtool eth1 Settings for eth1: Supported ports: [ TP MII ] 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 【摘要】 Ethtool 实用程序用于查看和更改以太网设备参数。1. 列出以太网设备属性当您使用设备名称执行 ethtool 命令时，它会显示有关以太网设备的以下信息。# ethtool eth0Settings for eth0: Supported ports: [ TP ] Supported link modes: 10baseT/Half 10baseT/Fu Hello, I have been trying to configure my Mellanox NIC (MCX512A-ACAT) in order to have a 10G-BASE SR connection using SFP and fiber optic cables, to another board (a custom made board that supports the same type of connections). 驱动程序未正确安装如果没有检测到ST-LINK设备，很可能是驱动 drv probe link ifdown ifup rx_err tx_err Link detected: yes When I check the server that has BAD connectivity problems I see a lot different: Settings for eth0: Supported ports: [ ] Supported link modes: Not reported Supported pause frame use: Symmetric Supports auto-negotiation: Yes Supported FEC modes: Not reported Advertised link Explore the ethtool command in Linux, a powerful tool for retrieving and modifying network interface settings. 网口连接问题定位当发现网络无法连接时，我们通常会检查指定网口的状态是否正常，出现以下情况说明网口状态异常：速率和传输模式显示为 "Unknown" 链路状态检测 (Link detected)显示为 "No" 出现以上情形，可先对链路进行检查，例如网线是否松动，更换网线进行排查，进一步可以排查是否为网卡 ethtoolコマンドを実行して、[Speed]や[Duplex]の値がおかしいときは、以下のように強制的に修正して、状況が改善されるかどうかを確認する。 The device-tree setting has: ti,op-mode = <DP83869_SGMII_COPPER_ETHERNET>; The link in Linux does not automatically come up, ip link claims NO-CARRIER even when a cable is plugged in. 1. Specifically: Initially, during boot up, the ethernet link light is on As ubuntu boots up, the link l 引言在CentOS系统中，网卡故障是一个常见的问题，其中link状态为no尤其让人头疼。这种状态表明网卡没有检测到物理连接，可能是由于硬件故障、配置错误或驱动问题引起的。本文将详细解析CentOS网卡link状态为no的解决办法，帮助用户快速定位并解决问题。故障现象当您在CentOS系统中使用ip link 或 The link lights are working, the switch at the other end says the port is up, and the Intel management interface that also uses the onboard NIC is working. A connected switch also shows a 1Gb link. But my Hello, under Debian 10 I have a very strange problem: eth0 goes down intermittently, without any errors and randomly; it just goes down, ip link reports "no carrier", ethtool shows "Link detected: no" and tcpdump shows no packets at all If I do a "ethtool -r eth0" link comes up again; the same The link lights are working, the switch at the other end says the port is up, and the Intel management interface that also uses the onboard NIC is working. for somehow, "Link detected" is not stable (it's stable if I remove bonding). When checking with the ifconfig the eth is shown but when checking with the ethtool it shows the link is off. So far, so good. By issuing ethtool -s eth1 autoneg off speed 1000 duplex full the link comes up. I can make everything work as normal by doing ip link set eno1 up and ifup vmbr0 at Learn how to use the ethtool command in Linux to manage network interfaces effectively. 7 其它 (1) 停止网卡的发送模块TX，请输入： ethtool -A tx off eth0 操作完毕后，可输入：ethtool -a eth0，查看tx模块是否已被停止。 (2) 关闭网卡对收到的数据包的校验功能，请输入 . You can replace it with USB dongle (wireless or wired). will routing table be identical in these two cases? Will ethtool or something else show the same linux-networking Problem: No link detected for eth2 (Engineer says, all lights showing green for eth2 on the switch. The tutorial I used stated to use ethtool to change wol settings. and bonding is working fine. On the other hand, in a virtual machine the link speed or duplex mode is usually meaningless, as the network interface is most often just a virtual link to the host system, with no actual physical Link detected: yes In the command above, we use ethtool to obtain the device properties of the enp0s3 network interface. <--- failover setup, but eth2 link/cable not detected by OS I understand there is no cable connected for eth2. For clarity : You are running latest firmware for your motherboard, have configured If autoneg is turned off, the 'Link detected' changes to yes, but speed and duplex remain unknown and it doesn't work still. 04 it does not detect the link Here's the output of ethtool eth0: Settings for eth0: Supported ports: [ TP MII ] I have an interesting issue. 0 and later Oracle Cloud Infrastructure - Version N/A and later Linux x86-64 Symptoms "ethtool" shows "Link detected: no" for a particular interface. I have the following problems: I cannot set speed, duplex or autoneg via ethtool, using sudo/root. the switch's port burned down, or someone tripped over a wire). Whether you are trying to troubleshoot a connectivity issue, verify the link speed, or simply document the current network configuration for 今回の例では、実行の結果、下記の赤字の箇所のように Link detected: no となっており、リンクがダウンしています。また Speed: 10Mb/s でリンク速度が 10M になっていました。 Supports Wake-on: pg Wake-on: g Link detected: yes これはケーブルがつながっているときですが、ケーブルが抜けていると、最後の行が"Link detected: no"という表示に変わります。これを使って、ケーブルがつながっていなければ、DHCPを使わないようにしてみましょう。 The reason was that both Speed and Duplex were not set and I needed to use ethtool to set the speed to 100 Mb/s and duplex to full: sudo ethtool -s <adapter_name> speed 100 duplex full where <adapter_name> is the name that shows for the adapter when using ip "ethtool" が "Link detected: no" をあるインターフェイスに対して出力します。 #ethtool eth0 Settings for eth0: 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 Hi, sorry to ask, I'm a bit clueless. when restarting the computer i see the link lights are on and green. Restart networking service or 文章浏览阅读5. I want to connect it at 40gbps to an Arista 7050TX-72Q switch. But what if my monitoring software checks every five Trying to install Firmware update on a Mellenox ConnectX3-Pro with Ubuntu 24. 6k次。本文介绍了Linux下ethtool工具，它可显示和更改网卡设置。详细说明了其显示网络端口设置功能，以及设置网卡协商模式的方法，并给出多个使用实例。还列举了ethtool的命令描述、使用概要和相关参考，包括保存设置的方法。背景：机房需要新增机器，机器网口太多，只接一根线需要确定接线网口位置。 1、使用 ethtool ethtool 是一个用于查询和控制网络接口设置的命令行工具。 [root@localhost ~]# ethtool ens37|grep Link Link detected: no[root@l ethtool是Linux下管理以太网卡配置的工具，可查询或修改网卡参数如速度、双工模式、Offload功能等。支持查看驱动信息、统计信息、执行自检等操作，通过命令行参数灵活控制网卡设置，适用于网络性能调优和故障排查。了解了 ethtool_get_link 子函数的部分代码，我们可以发现，上文中提到的在网卡接口 down 的状态下进行自协商后，phy 的状态变为 UP，而 ethtool 输出的 Link detected 项为 no 的情况是正常的现象。 hello i have just added a new NIC to the server. Cause This looks like a low level issue that originates long before high level tools like systemd-networkd and NetworkManager play a role. But there is another way to tell. 0-xilinx-v2021. I can make everything work as normal by doing ip link set eno1 up and ifup vmbr0 at However, I don't think that's your entire problem, because eno1 has no link detected with ethtool, and ethtool should show a link for an online などの状態が確認できます。また、ethtoolコマンドは多数のオプションを有しており、たとえば「#ethtool -i eth0」のように「-i」オプションを使用することで、NICに適用されているドライバ名やバージョン、デバイスのバス番号を表示させることが With copper Ethernet you can see if there's a physical link even when the NIC is unused, i. Your virtual machine probably emulates a very primitive network adapter and not much data is available. Tried it on Ubuntu and RHEL7 VM. I ran an ethernet cable as a temp measure and it's finally time for me to troubleshoot the problem. This port named eth0 should run at 1 Gbit/sec speed (at least the d In this example, we use the ethtool command followed by the name of the network interface, eth0. Allen Hi, I'm trying this on a u250, which has 2 QSFP+ ports. My question is, how can I quickly test the physical condition or state of this a fibre connection I was trying to setup Wake-on-LAN. 参考文档好的参考文档： lnmp: ethtool1. All three cards are running in ETH mode. pbxp zaqjv yyvy bbiecgcl gwyf ftdkq bmvi dhntm naj qiv