Linux bridge interface centos

CentoOS 7 настройка bridge

Всем доброго времени суток. В Linux новичок. Хочу настроить bridge для последующего использования kvm. Есть сетевой интерфейс enp1s0f0 .

Помогите понять в чем проблема

ip ro что показывает? И DEFROUTE=yes у ethernet интрефейса убери.

Я может чего-то не понял, но почему у тебя PREFIX=32?

У тебя нет маршрута до шлюза, соответственно, нет и шлюза.

Тебе нужен другой префикс (маска подсети).

Эти настройки интерфейса были прописаны хостером. Я префикс менять не стал. Для сервера, как я понимаю, выделен 1 статический ip и соответственно префикс нет смысла указывать другой. Это же настройки для подключения к маршрутизатору хостера, а не для виртуальной подсети, или я не правильно мыслю?

Что-то у тебя вообще нет маршрутов из настраиваемой подсети. Можешь попробовать руками добавить ip ro add default via 89.XXX.XXX.XX

В обычной ситуации без всяких туннелей и т.п.:

• у тебя есть интерфейс с ip-адресом 1.2.3.4
• у тебя есть маска, например 24 (в твоём случае 32)
• по этой маске (24) строится маршрут, что все ip-адреса в диапазоне 1.2.3.1-1.2.3.254 ищутся в том же сегменте, что и интерфейс. В твоём случае 32 означает, что в том же сегменте может быть найден только сам интерфейс 1.2.3.4, и никаких других.
• устанавливается дефолтный шлюз 1.2.3.1.
• в случае с маской 24 он доступен, т.к. есть маршрут, по которому к нему можно обратиться. В твоём случае такого маршрута нет.
• далее рисуется маршрут о том, что ко всему, что не найдено надо обращаться через шлюз.

Как-то так. Я правильно понимаю, что без бриджа у тебя всё работает? В /etc/sysconfig/network-scripts/route-enp1s0f0 есть что-либо?

Попробуй заменить префикс на 24. Если поможет, то у провайдера нужно выяснить правильный префикс.

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3 Ways to Create a Network Bridge in RHEL/CentOS 8

A network bridge is a data-link layer device that interconnects two or more network segments, offering communication between them. It creates a single network interface to set up a single aggregate network from multiple networks or network segments. It forwards traffic based on the MAC addresses of hosts (stored in a MAC address table).

Linux operating systems such as RHEL (Red Hat Enterprise Linux) and CentOS 8 support the implementation of a software-based network bridge to emulate a hardware bridge. The bridge serves a similar function as a network switch; it acts more or less like a virtual network switch.

There are several use cases of network bridging, one practical application is in a virtualization environment to create a virtual network switch used to connect virtual machines (VMs) to the same network as the host.

This guide shows multiple ways to set up a network bridge in RHEL/CentOS 8 and use it to set up virtual networking in a bridged mode under Oracle VirtualBox and KVM, to connect Virtual Machines to the same network as the host.

On this page:

Setting Up a Network Bridge Using nmcli Tool

nmcli is a widely-used, scriptable and powerful command-line tool to control NetworkManager and report network status. It communicates directly to NetworkManager and controls only system-wide connections. Importantly, it allows users to use abbreviations, as long as they are a unique prefix in the set of possible options.

First, use the IP command to identify the network interfaces (both physical and virtual) currently attached to your machine and the networks they are connected to.

From the output of the above command, the Ethernet interface is called enp2s0, we will add this interface to the bridge as a slave.

Check Network Interfaces

Next, to list the active network connections on the test system, use the following nmcli command.

List Active Network Connections

Important: If the libvirtd daemon (libvirtd) is installed and started, the default network interface that represents the network bridge (virtual network switch) is virbr0 as seen in the above screenshots. It is configured to run in NAT mode.

Next, create a network bridge interface using the following nmcli command, where conn or con stands for connection, and the connection name is br0 and the interface name is also br0.

Create Network Bridge Interface

Note: In a bridged mode, the virtual machines are easily accessible to the physical network, they appear within the same subnet as the host machine and they can access services such as DHCP.

To set a static IP address, run the following commands to set IPv4 address, network mask, default gateway, and DNS server of the br0 connection (set the values according to your environment).

Now add the Ethernet interface (enp2s0) as a portable device to the bridge (br0) connection as shown.

Add Ethernet Interface as a Slave to Bridge

Next, bring up or activate the bridge connection, you can use the connection name or UUID as shown.

Active Network Bridge Connection

Then deactivate or bring down the Ethernet or Wired connection.

De-active Network Wired Connection

Now when you try to list the active network connections on the system, the bridge connection should display on the list.

List Active Network Connection

Next, use the following bridge command to display the current bridge port configuration and flags.

Show Bridge Ports

To deactivate the bridge connection and delete it, run the following commands. Note that you first of all have to activate the wired connection.

Delete Bridge Network Connection

For more information, see the nmcli manual page.

Creating a Network Bridge via Cockpit Web Console

The cockpit is a lightweight, interactive and easy-to-use web-based server administration interface. To interact with the system’s network configuration, the cockpit uses NetworkManager and the DBus APIs it provides.

To add a bridge, go to Networking, then click Add Bridge as highlighted in the following image.

Choose Networking in Cockpit Web Console

A pop window with options to add a new bridge will appear. Set the bridge name and select the ports as shown in the following screenshot. You can optionally enable STP (Spanning Tree Protocol) and then click Apply.

Add Network Bridge Settings

Under the list of Interfaces, the new bridge should now appear and the Ethernet interface should be de-activated.

New Network Bridge Interface

To view the bridge in detail, double click on it. There are options to take it down or delete, add a new port device to it and more.

View Network Bridge Details

Creating a Network Bridge Using nm-connection-editor Application

nm-connection-editor is a graphical network connection editor for NetworkManager, used to add, remove, and modify network connections stored by NetworkManager. Any modifications can only work if NetworkManager is running.

To launch it, run the nm-connection-editor command as root in the command line or open it from the system menu.

Once it opens up, click the plus sign to add a new connection as highlighted in the following screenshot.

Add a New Network Connection

From the pop window, choose the connection type from the drop-down, Bridge in this case and click Create.

Choose Network Connection Type

Next, set a bridge connection and interface name, then click Add to add a bridge port. Choose Ethernet as the connection type. Then click Create.

Create a Bridge Connection Choose Ethernet as Connection Type

Next, edit the port device connection details and click Save.

Edit Network Bridge Port

Now the bridged port should be added to the list of bridged connections. Then click Save.

Network Bridge Port Added

From the connection editor’s main interface, you should be able to see the new bridged connection and bridge interface as shown in the following screenshot.

Network Bridge Created Successfully

Now go ahead to activate the bridge connection and deactivate the wired connection from the command line using the nmcli tool as shown before.

How to Use the Network Bridge in a Virtualization Software

In this section, we will show how to use a bridge to connect virtual machines to the host network, under Oracle VirtualBox and KVM as explained below.

Using a Network Bridge in Oracle VirtualBox

To configure a virtual machine to use a bridged adapter, select it from the list of VMs, then go to its settings, click Network option and select the adapter (e.g Adapter 1), then make sure the Enable Network Adapter option is checked, set the attached to as Bridged Adapter, then select the name of the bridged interface (br0) and click Ok.

Configure VM to Use Bridge Network in VirtualBox

Using a Network Bridge in KVM

To use the network bridge created above under KVM, use the —network=bridge=br0 option while virtual machines using the command-line interface, using the virt-install command.

You can as well create additional networks and configure them using the virsh command-line tool, and a VM’s XML configuration file can be edited to use one of these new bridged networks.

In this guide, we have shown how to set up a network bridge in RHEL/CentOS 8 and use it within to connect VMs to the same network of the host, under Oracle VirtualBox and KVM.

As usual, reach us via the feedback form below for any questions or comments. You can find more details in understanding virtual networking and configuring a network bridge in RHEL 8 documentation.

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How to create or configure network bridge in CentOS / RHEL 7/8

Table of Contents

In my last article I shared the steps to configure NIC Teaming on RHEL/CentOS 7 Linux . In this article I will show you step by step guide to configure network bridge using nmtui (NetworkManager) on CentOS or RHEL 7 node. A network bridge is a Link Layer device which forwards traffic between networks based on MAC addresses and is therefore also refer to as a Layer 2 device. Bridge networking (also known as network bridging or virtual network switching) will place virtual machine network interfaces on the same network as the physical interface.

You can configure network bridge using NetworkManager Text User Interface (NMTUI) or via Command Line Interface (CLI) by manually creating the required configuration files. I have written another article to configure network bridge on Oracle Virtual Box .

Configure Network Bridge using NMTUI (NetworkManager)

The text user interface tool nmtui can be used to configure network bridge in a terminal window. Issue the following command to start the tool:

The text user interface appears. Any invalid command prints a usage message.

From the starting menu, select Edit a connection. Select Add, the New Connection screen opens.

Select Bridge using which you wish to configure network bridge, the Edit connection screen opens.

Give a Profile name and Device name to the bridge.

To add slave interfaces to the bridge select Add, the New Connection screen opens.

Enter the required slave’s device name or MAC address in the Device section and select the OK button.

The name of the bridge slave appears in the Slaves section.

If you have a DHCP server then you can leave the IPv4 and IPv6 Address set to «Automatic«. If you wish to assign static IP then manually fill in the network details as shown below. Since we are not using IPv6 so I have set IPv6 Configuration as Ignore.

Review and confirm the settings before selecting the OK button which will exit the nmtui (NetworkManager) utility..

Next restart your network services for the changes to take affect.

Now check your network configuration

Finally now we will validate our bridge connectivity

So we can connect to our gateway which means our bridge is working as expected.

Configure network bridge via CLI

To configure network bridge, create a file in the /etc/sysconfig/network-scripts/ directory called ifcfg-brN , replacing N with the number for the interface, such as 0. For our case we will create ifcfg-br1

The contents of the bridge interface file and ethernet interface file is almost. The differences in this example are as follows:

• The DEVICE directive is given an interface name as its argument in the format brN , where N is replaced with the number of the interface.
• The TYPE directive is given an argument Bridge. This directive determines the device type and the argument is case sensitive.
• The bridge interface configuration file now has the IP address and the physical interface has only a MAC address.
• An extra directive, DELAY=0 , is added to prevent the bridge from waiting while it monitors traffic, learns where hosts are located, and builds a table of MAC addresses on which to base its filtering decisions.
• Add NM_CONTROLLED=no to the Ethernet interface to prevent NetworkManager from altering the file.

The following is a sample bridge interface configuration file using a static IP address:

To complete network bridge we must create another interface, or you can use an existing interface, and point it to the bridge interface. The following is a sample Ethernet interface configuration file pointing to a bridge interface. Configure your physical interface in /etc/sysconfig/network-scripts/ifcfg-ethX , where X is a unique number corresponding to a specific interface, as follows:

Finally restart your network service for the changes to take affect

I hope the article to configure network bridge using NetworkManager nmtui on RHEL/CentOS 7/8 Linux was useful. Please let me know your feedback and views using the comment box below.

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