How to use Linux for virtual network configuration

With the increasing popularity of technologies such as cloud computing, big data and the Internet of Things, virtualization technology has become a hot topic in today's IT field. Virtualization is a method of sharing and managing resources by dividing a physical host into multiple independent virtual machines. Virtual network is an important component of virtualization and can meet the network isolation and interaction needs between different applications. In this article, we will explain how to use Linux for virtual network configuration.

1. Overview of Linux virtual network

In the physical network, the network card is the bridge connecting network devices. In a virtual network, the virtual network card replaces the physical network card, allowing the virtual machine to connect to the physical network through the virtual network card. At the same time, virtual Switch (vSwitch) replaces the physical switch and realizes communication between virtual machines and communication between virtual machines and the physical network.

In Linux, a virtual network is implemented by a set of tools and services. QEMU (Quick EMUlator) is an open source virtualization tool that can simulate the hardware environment of different operating systems. KVM (Kernel-based Virtual Machine) is a virtualization technology provided by the Linux kernel, which can extend virtualization to the hardware level. Libvirt is a toolkit for managing virtualization. It provides a set of APIs and tools for controlling the creation, deletion, and startup of virtual machines.

2. Create a virtual network

In Linux, there are many ways to create a virtual network. Among them, you can quickly create a virtual network using the virsh command provided by libvirt. The following is an example of the creation command:

$ sudo virsh net-define /path/to/network.xml
$ sudo virsh net-autostart network -name
$ sudo virsh net-start network-name

Among them, /path/to/network.xml is the configuration file of the virtual network, and network-name is the name of the virtual network.

The configuration file of a virtual network usually includes the following information:

(1) Network name and UUID
(2) Network type, such as NAT or bridging
(3) IP address Range and subnet mask
(4) DHCP options for automatically assigning IP addresses
(5) Connection method between physical host and virtual machine, such as bridging or NAT

via the above command After creating the virtual network, we can use the following commands to view the status and configuration information of the virtual network:

$ sudo virsh net-list --all
$ sudo virsh net-dumpxml network-name
$ sudo virsh net-info network-name

3. Create a virtual machine

After creating the virtual network, we need to create the virtual machine and connect it to the virtual network. The following is an example of using QEMU to create a virtual machine:

$ sudo qemu-img create -f qcow2 /path/to/disk-image.qcow2 10G
$ sudo qemu-system-x86_64 -enable-kvm -m 2048 -boot c -drive file=/path/to/disk-image.qcow2 -net nic,model=virtio -net tap,ifname=tap0,script=no,downscript=no

Among them, The qemu-img command is used to create a disk image file, and the qemu-system-x86_64 command is used to start a virtual machine.

You may notice that there is a -tap option in the above startup command. This is used to create and manage virtual network cards and connect them to virtual networks. The TAP device is a virtual network device and a network interface provided by the Linux kernel that can connect a virtual machine to a virtual network.

In the above startup command, we use the virtio driver of the virtual network card, which is a high-performance virtualized network device with lower latency and higher throughput in network transmission. In addition, we also specified the name of the virtual network card as tap0, which can be viewed through the ifconfig command or ip command of the Linux kernel.

4. Summary

Virtual network is one of the infrastructures for virtualization. It can help us achieve network isolation between virtual machines, communication between virtual machines and physical networks, etc. need. The configuration of a virtual network involves multiple components, including virtual network cards, virtual switches, and network services. In Linux, we can use tools such as QEMU, KVM, and libvirt to quickly create and manage virtual networks and virtual machines. Through these configuration methods, we can efficiently utilize computing resources and achieve effective communication and isolation between different applications.

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