Network configuration in Linux 2021-10-29

Keywords: Linux Operation & Maintenance network

IP and subnet mask concepts

1. What is IP ADDRESS

internet protocol ADDRESS ## network process address
ipv4 internet protocol version 4

ip is composed of 32 01s
11111110.11111110.11111110.11111110 = 254.254.254.254

2. Subnet mask
Used to divide the network area
The number on the ip corresponding to the non-zero bit of the subnet mask represents the network bit of this ip
The number corresponding to bit 0 of the subnet mask is the host bit of the ip
The network bit represents the network area
The host bit represents a host in the network area

3.ip communication judgment
Two IP S with the same network bit and inconsistent host bit can communicate directly
172.25.254.1/24 (24=255.255.255.0)
172.25.254.2/24
172.25.0.1/16 cannot communicate with the above ip

2, Temporary management network card

Note: it is called temporary. When the network card is restarted, the configuration is restored to its original appearance
1. Related commands

ip a   		##View ip information
ifconfig    ##View ip information

ping 		##Check whether the network is unobstructed
ping -c 1 	##Ping once
ping -w 1 	##Wait 1 second
ping -c1 -w1 ip ##ping1 time, wait 1 second

ifconfig	 ##View or set network interface
ifconfig 	 ##see
ifconfig device ip/24 		##set up
ifconfig device down 		##close
ifconfig device up  		##open

ip addr ##Detect or this network interface
ip addr show ##testing
ip addr add ip/24 dev device ##set up
ip addr del dev ens160 ip/24 ##delete

"Note: the name of the device is a physical fact. You can only use what life word you see, such as ens3

3, Permanent management network card

Make sure the service is turned on first

1. Set the network graphically

nm-connection-editor  		  #####Open graphics
nmcli connection shoW    	  ######Displays information about network links
nmcli connection down westos  ######Turn off the westos network card
nmcli connection reload       #####Refresh link
nmcli connection up westos    #####Restart the specified connection

Note: change is different from direct creation. If it is new, it will take effect directly
The changes are only saved, but the configuration file cannot take effect immediately. It needs to be reloaded with the command. You can see the operation in the following picture

2. Image configuration network based on nmtui text model

Note: in this way, the newly created network configuration will take effect immediately. If you change it, you need to command reload to take effect

3. nmcli command mode setting network

nmcli ##NetworkManager must be enabled

nmcli device connect ens3 	 ##Enable ens160 network card
nmcli device disconnect ens3 ##Turn off the network card
nmcli device show ens3		 ##View network card information
nmcli device status ens3     ##View network card service interface information

nmcli connection show        ##View connections
nmcli connection down westos ##Close connection
nmcli connection up westos   ##Open connection
nmcli connection delete westos ##Delete connection

#add connections
nmcli connection add type ethernet con-name westos ifname ens160 ip4 172.25.254.100/24

#change
nmcli connection modify westos ipv4.addresses 172.25.254.200/24

When there is no graphic operation, the modification of ip can not take effect immediately. It is still the old method

4. Set up the network by managing the network profile

The network configuration directory is in / etc / sysconfig / network scripts/
The configuration file must start with ifcfg -, such as ifcgf-ens3

Some contents in the document:

.	explain
DEVICE= xxx	Equipment name xxx
ONBOOT=yes	Automatically activate the network card when the network service is turned on
BOOTPROTO=dhcp or static or none	Equipment working mode
IPADDR =	IP address
PREFIX =	Subnet mask
NETMASK=	It's also a subnet mask. Just select one from the above
NAME=	Interface name

Two IPS are configured on one piece (mult ip le can be configured, but too many are unnecessary)

After saving and exiting vim, you also need to reload the network

4, Gateway settings

Add temporary gateway

ip route add default via ip

Set global gateway

vim /etc/sysconfig/network

The experiment requires two virtual hosts, in which westosa sets up a dual network card as a router and westosb sets up a single network card
```
vim /etc/sysconfig/nrtwork-scripts
```

Reload the classic configuration

Use the ping command to see if the ip address is set correctly
The real machine is 172.25.254.72
westosa has two ip addresses:
172.25.254.100
1.1.1.100
westosb ip: 1.1.1.200
Use westosa to ping the real machine and westosb respectively. After ok, proceed to the next step

Supplement: configure the gateway with the specified IP effective
That is, it only works for one network card, such as ens3
Modify the / etc / sysconfig / network scripts / ifcfg-ens3 file with vim
Add a row

After setting the gateway, the dns operation will be supplemented next time...