What does lo mean in centos?

In centos, lo is the abbreviation of loopback, which means loopback interface; the loopback interface is used as a local software loopback to test the communication between the host processes and detect the network configuration of the local machine. Some applications need to call resources on the server when running, and the IP of lo can only be "127.0.0.1".

The operating environment of this article: centos 7 system, Dell G3 computer.

What does lo mean in centos

In centOS7, the ifconfig command has been officially abolished, so the network card cannot be found with this command. We use ip addr in centOS to check our Internet Information.

lo is the loopback interface. virbr is a virtual bridge (Virtual Bridge), and virbr0 is a virtual bridge network card. Generally, the default network card before centos6.5 is eth0, and after centos7, ensxx (xx is a number). Of course, there are also network card names that have been modified. The loopback interface is used for local software loopback testing of communication between processes on this host. To simply understand, it is used for local testing, and its inet, that is, ip, can only be 127.0.0.1.

For example, in my centos7 version, the default network card name is ens33, and in the centos6.5 version, the default network card name is eth0.

In the virtual machine, some network card names are eth1 or eth2, indicating that the virtual image is copied. Since the network card eth0 in the physical machine automatically recognizes the MAC address of the physical machine, it runs in the virtual machine. The network card name will automatically become eth1. If you copy this virtual image and run it on another computer, the network card name will become eth2. But you can also modify the ifcfg-eth0 configuration file, bind the MAC address, delete the /etc/udev/rules.d/70-persistent-net.rules configuration file, and restart to take effect.

lo has two main functions:

The first is to test the network configuration of this machine. If it can PING 127.0.0.1, it means that there is no problem with the network card and IP protocol installation of this machine;

Another function is that some SERVER/CLIENT applications need to call resources on the server when running

Recommended tutorial: "centos tutorial"

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