What is eth0 in linux

/etc/network/interfaces Ubuntu Linux networking example

Q . Can you explain how to setup network parameters such as IP address, subnet, dhcp etc using /etc/network/interfaces file?

A . /etc/network/interfaces file contains network interface configuration information for the both Ubuntu and Debian Linux. This is where you configure how your system is connected to the network.

Defining physical interfaces such as eth0

Lines beginning with the word “auto” are used to identify the physical interfaces to be brought up when ifup is run with the -a option. (This option is used by the system boot scripts.) Physical interface names should follow the word “auto” on the same line. There can be multiple “auto” stanzas. ifup brings the named inter faces up in the order listed. For example following example setup eth0 (first network interface card) with 192.168.1.5 IP address and gateway (router) to 192.168.1.254:
iface eth0 inet static
address 192.168.1.5
netmask 255.255.255.0
gateway 192.168.1.254

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Setup interface to dhcp

To setup eth0 to dhcp, enter:
auto eth0
iface eth0 inet dhcp

Examples: How to set up interfaces

Following is file located at /usr/share/doc/ifupdown/examples/network-interfaces , use this file as reference (don’t forget interfaces man pages for more help):

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How to Rename ethernet interface to eth0 in Linux

Today again I am going to discuss 1 more issue which I faced recently with Oracle Enterprise Linux – 6.3, maybe there are many who might have faced this already.

So let me discuss the problem first.

What’d caused the issue?
— I copied my VM Ware Machine- A from my current laptop to different laptop and when I started it, my default eth0 was not coming up.
— So I decided to delete this from VM Ware Setting and add a new Adapter and I did the same and started my Machine, I did not realize but I did this 2-3 times.
— So finally what I got this is my ethernet name was changed to eth3 though my configuration file which was ifcfg-eth0 before, was mistakenly deleted by me. The situation was like below:

Even though I tried starting my network but it was not coming up.

What I did to sort out my problem:

I created ifcfg-eth0 file manually, and the configuration file of eth0 was like the below:

I again tried to restart my network and it started this time, however, the ifconfig was still showing eth3, however, the configuration file eth0 was picked up.

Now, my motive was to change the name eth3 to eth0, for anyone it could be eth1 to eth0 or eth2-eth0, for me it was like eth3 to eth1.

Renaming your network interface to eth0:

Oracle Enterprise Linux, with many others, stores the network interface hardware configuration using udev. The network interface configuration is stored in the file /etc/udev/rules.d/70-persistent-net.rules. Open this file with editor (vim) and start editing. You’ll see configuration lines, like:

As you can see, the system now has the configuration for four interfaces: eth0,eth1,eth2 and eth3. The eth0,eth1 and eth2 line contain the hardware (MAC) address of the old network card, the fourth line is the new one. Because your network configuration scripts (where IP address settings are stored) are bound to a specific device (eth0) and the system doesn’t know about eth1, it can’t bring it up. To fix this, simply rename “eth3″ to “eth0″ in the NAME field, and remove or comment other lines.

Updating hardware MAC address in networking script:

Apart from the hardware configuration, there is also a networking configuration for the interface. This configuration is stored in /etc/sysconfig/network-scripts/ifcfg-eth0. In this file the IP address configuration is bound to the specific interface. This file most of the times also contains a specific hardware address, the MAC address of the interface the IP address should bind to. Look for the “HWADDR” line and update its value to the one you wrote down earlier from the udev configuration.

Reboot the system to update ethernet numbering.

Now check ifconfig and you will get what you expect.

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Шпаргалка по настройке сети в Linux

Что за компьютер без подключения к сети и к Интернету, в частности? Данная шпаргалка поможет настроить сетевые интерфейсы в Линуксе, а для примера будет взят Debian.

И так, в самом начале необходимо удостовериться, что ваша сетевая карта в компьютере обнаружена ОС, для этого выполним команду:

dmesg | grep -i Eth или же lspci | grep Ether – для поиска вводится начало «eth», т.к. сетевой карте (Ethernet) обычно присваивается интерфейс под названием eth0, где 0 – номер устройства. Если сетевых карт в компьютере несколько, то должно быть, соответственно, eth0, eth1, eth2 и т.д. В итоге на консоль должно быть выведено что-то вроде такого:

[ 1.326482] forcedeth: Reverse Engineered nForce ethernet driver. Version 0.64.
[ 1.328138] forcedeth 0000:00:0a.0: PCI INT A -> Link[LMAC] -> GSI 22 (level, low) -> IRQ 22
[ 1.328225] forcedeth 0000:00:0a.0: setting latency timer to 64
[ 1.853889] forcedeth 0000:00:0a.0: ifname eth0, PHY OUI 0x732 @ 1, addr 00:1d:60:47:8f:78
[ 1.853982] forcedeth 0000:00:0a.0: highdma pwrctl mgmt lnktim msi desc-v3
[ 34.458536] forcedeth 0000:00:0a.0: irq 42 for MSI/MSI-X
[ 34.458756] eth0: no link during initialization.
[ 34.459691] ADDRCONF(NETDEV_UP): eth0: link is not ready

Как видно из приведенного примера, в компьютере установлена сетевая карта от nVidia c драйвером 0.64 и с присвоенным интерфейсом под названием eth0, правда, он в данный момент не активен, т.к. отсутствует соединение кабеля к сетевой плате.

Теперь можно ввести в консоль следующую команду для отображения информации о сетевых интерфейсах:

На что она нам покажет:

eth0 Link encap:Ethernet HWaddr 00:1d:60:47:8f:78
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
Interrupt:42 Base address:0xa000

lo Link encap:Локальная петля (Loopback)
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:122 errors:0 dropped:0 overruns:0 frame:0
TX packets:122 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:12867 (12.8 KB) TX bytes:12867 (12.8 KB)

Первый интерфейс – это eth0, с MAC-адресом 00:1d:60:47:8f:78. Т.к. в описании интерфейса отсутствует слово RUNNING, то это означает, что сетевой кабель не подключен. Второй интерфейс, присутствующий в списке – это lo, локальный интерфейс (т.н. называемый Loopback), который имеет фиксированный для всех loopback-интерфейсов IP-адрес 127.0.0.1, маску подсети 255.0.0.0 и статус RUNNING. Из всего приведенного видно, что сетевой интерфейс eth0, который нам нужен для организации сети и выхода в Интернет, не настроен. Сейчас мы этим и займемся.

Нам необходимо отредактировать файл конфигурации /etc/init.d/networking, но в Debian’e его нельзя редактировать до тех пор, пока не остановлены сетевые интерфейсы. Поэтому нужно отключить интерфейс:

Однако, у нас же еще интерфейс eth0 не сконфигурирован, поэтому мы получим сообщение об ошибке: ifdown: interface eth0 not configured. Тогда, для начала, проверяем существование файла /etc/network/interfaces. Если он не существует, то создадим его, а если существует, то отредактируем:

На экран консоли должно вывестись примерно следующее:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
#iface eth0 inet dhcp

Если у вас есть маршрутизатор с включенной функцией DHCP (т.е. происходит автоматическая раздача IP-адресов для подключающихся устройств), то достаточно в конфигурационном файле разкомментировать строку #iface eth0 inet dhcp. В противном случае, необходимо привести файл конфигурации к следующему виду:

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet static
address 192.168.1.2
netmask 255.255.255.0
gateway 192.168.1.1
dns-nameservers 8.8.8.8 8.8.4.4
#iface eth0 inet dhcp

Adress – это IP-адрес, который вы присваиваете сетевой карте на интерфейсе eth0, netmask – маска подсети, gateway – шлюз, dns-nameservers – адреса DNS-серверов. Теперь необходимо активировать сетевой интерфейс:

А также перезапустить сетевые службы:

Теперь можно заново запустить команду ifconfig и убедиться, что интерфейс eth0 настроен, т.е. присутствуют указанные нами сетевые настройки. Для проверки работоспособности, можно пропинговать шлюз или интернет-ресурс, если у вас есть выход в Интернет:

ping 192.168.1.1 -с 5
ping yandex.ru -с 5

Должно быть выведено следующее:

PING yandex.ru (213.180.204.211) 56(84) bytes of data.
64 bytes from yandex.ru (213.180.204.211): icmp_req=1 ttl=50 time=15.1 ms
64 bytes from yandex.ru (213.180.204.211): icmp_req=2 ttl=50 time=14.1 ms
64 bytes from yandex.ru (213.180.204.211): icmp_req=3 ttl=50 time=14.3 ms
64 bytes from yandex.ru (213.180.204.211): icmp_req=4 ttl=50 time=13.8 ms
64 bytes from yandex.ru (213.180.204.211): icmp_req=5 ttl=50 time=13.9 ms

— yandex.ru ping statistics —
5 packets transmitted, 5 received, 0% packet loss, time 4006ms
rtt min/avg/max/mdev = 13.804/14.286/15.125/0.479 ms

На этом настройка сети в Линуксе завершена.

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What is eth0 in Linux?

eth0 is the first Ethernet interface. (Additional Ethernet interfaces would be named eth1, eth2, etc.) This type of interface is usually a NIC connected to the network by a category 5 cable. lo is the loopback interface. This is a special network interface that the system uses to communicate with itself.

How do I start eth0 in Linux?

How to Enable an Network Interface. The “up” or “ifup” flag with interface name (eth0) activates an network interface, if it is not in active state and allowing to send and receive information. For example, “ifconfig eth0 up” or “ifup eth0” will activate the eth0 interface.

Where is eth0 in Linux?

You can use the ifconfig command or ip command with grep command and other filters to find out an IP address assigned to eth0 and display it on screen.

What is the difference between the eth0 and lo interface?

eth0 is a physical interface representing Ethernet network card. It’s used for communication with other computers on the network and on the Internet. lo is a special virtual network interface called loopback device.

How do you know if its eth0 or eth1?

If only one Ethernet adapter is installed, that adapter is defined as eth0 . If the Ethernet adapter is a dual port Ethernet adapter, then the port labeled Act/link A will be eth0 . The port labeled Act/link B would be eth1 .

How do I find my IP in Linux?

The following commands will get you the private IP address of your interfaces:

1. ifconfig -a.
2. ip addr (ip a)
3. hostname -I | awk ‘’
4. ip route get 1.2. …
5. (Fedora) Wifi-Settings→ click the setting icon next to the Wifi name that you are connected to → Ipv4 and Ipv6 both can be seen.
6. nmcli -p device show.

How do I bring down an interface in Linux?

Two methods can be used to bring interfaces up or down.

1. 2.1. Using “ip” Usage: # ip link set dev up # ip link set dev down. Example: # ip link set dev eth0 up # ip link set dev eth0 down.
2. 2.2. Using “ifconfig” Usage: # /sbin/ifconfig up # /sbin/ifconfig down.

How do I check Ethernet status?

1. Press Windows + R and type “cpl”. The command should work on various Windows OS versions.
2. Right Click on “Ethernet or Local Area Connection” and Click on “Status”

How do I enable Ethernet on Linux?

1. Open a terminal by pressing Ctrl + Alt + T .
2. In the terminal, type sudo ip link set down eth0 .
3. Enter your password when prompted and hit Enter (NOTE: you will not see anything being entered. …
4. Now, enable the Ethernet adapter by running sudo ip link set up eth0 .

How do I see all interfaces in Linux?

ifconfig command – It is used to display or configure a network interface.

1. List Network Interfaces Using ip Command on Linux. …
2. Linux show / display available network interfaces using nmcli. …
3. Show a table of all network interfaces using netstat command in Linux. …
4. Linux ip list interfaces using ifconfig command.

What is IP loopback address?

A loopback address is a special IP address, 127.0. 0.1, reserved by InterNIC for use in testing network cards. … The loopback address allows for a reliable method of testing the functionality of an Ethernet card and its drivers and software without a physical network.

What does eth1 mean?

eth1 is the onboard Ethernet (wired) adapter on your Linux machine. eno1 is your embedded NIC (onboard Network Interface Card). It is a regular physical network interface. You can use this link as reference. This is a way of representing the Ethernet names.

What is the output of ifconfig?

Nevertheless, the ifconfig output shows that three forms of addresses are currently assigned to qfe0: loopback (lo0), IPv4 (inet), and IPv6 (inet6). In the IPv6 section of the output, note that the line for interface qfe0 displays the link-local IPv6 address.

What is enp0s3 Ubuntu?

it stands for “ethernet network peripheral # serial #”

What Ifconfig shows?

For starters, ifconfig stands for “interface configuration”. The command provides options for viewing as well as changing your network settings. By itself (no options), the ifconfig command shows active network interfaces (you may have others).

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