Linux Basics - Network management of the network interface

First, network management

1. Network Status View: ip addr (ifconfig)

1.1 net-tools (centos 7 previous version) VS iproute2 (Centos recommended after 7)

1.1.1 net-tools (centos 7 previous version)

• ifconfig # Network Interface Management Command
  network interface naming conventions: CentOS 7 uses a consistent network device naming

  Network Interface Name	NIC type
  en01	Onboard LAN
  ens33	PCI-E card
  enp0s3	Unable to get a physical card PCI-E card
  eth0	In addition to these card types

Example:

 `查看所有接口信息`
[root@localhost ~]# ifconfig -a 
ens32: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.5.128  netmask 255.255.255.0  broadcast 192.168.5.255
        inet6 fe80::20c:29ff:fe12:dd9c  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:12:dd:9c  txqueuelen 1000  (Ethernet)
        RX packets 373  bytes 35292 (34.4 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 322  bytes 48941 (47.7 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 140  bytes 14788 (14.4 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 140  bytes 14788 (14.4 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

"网络接口启用/停用":'使用远程终端连接小心停用网络接口'
[root@localhost ~]# ifconfig [dev-name] [up|down]
dev-name :网络接口名称，如，ens32

• route # route setting commands
  routecommands by default IP resolves domain name or service name, so the speed will be very slow, use route -ncan not resolve domain names, speed up response time; as follows:
  

  [root@localhost ~]# time route
  Kernel IP routing table
  Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  default         gateway         0.0.0.0         UG    100    0        0 eth0
  192.168.5.0     0.0.0.0         255.255.255.0   U     100    0        0 eth0
  192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0
  
  real    0m0.010s
  user    0m0.000s
  sys     0m0.008s
  [root@localhost ~]# time route -n
  Kernel IP routing table
  Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
  0.0.0.0         192.168.5.2     0.0.0.0         UG    100    0        0 eth0
  192.168.5.0     0.0.0.0         255.255.255.0   U     100    0        0 eth0
  192.168.122.0   0.0.0.0         255.255.255.0   U     0      0        0 virbr0
  
  real    0m0.003s
  user    0m0.000s
  sys     0m0.004s
  

• netstat # Network Socket View

1.1.2 iproute2 (Centos 7 after the recommendation, superior net-tools)

• ip See: Linux foundation of basic network ip command
• ss See: Linux foundation of basic network command ss

1.1.3 Network Interface name changed toeth0

To modify a network interface commands ideas:

1. NIC naming and net.ifnames parameter limits by biosdevname

2. Modifying /etc/default/grubthe file, add the above parameters (biosdevname = 0 net.ifnames = 0) , as follows:
   

3. Use grubfile rebuild /boot/grub2/grub.cfgboot files, file location note grub.cfg

   [root@localhost ~]# grub2-mkconfig -o /boot/grub2/grub.cfg
   Generating grub configuration file ...
   Found linux image: /boot/vmlinuz-3.10.0-957.el7.x86_64
   Found initrd image: /boot/initramfs-3.10.0-957.el7.x86_64.img
   Found linux image: /boot/vmlinuz-0-rescue-b21899b2f3ce4b5c8d131cd0cb02811f
   Found initrd image: /boot/initramfs-0-rescue-b21899b2f3ce4b5c8d131cd0cb02811f.img
   done
   

4. Restart to take effect reboot

5. NIC view the modified name

   [root@localhost ~]# ifconfig
   `eth0`: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
           inet 192.168.5.128  netmask 255.255.255.0  broadcast 192.168.5.255
           inet6 fe80::f43f:e585:bceb:5680  prefixlen 64  scopeid 0x20<link>
           ether 00:0c:29:12:dd:9c  txqueuelen 1000  (Ethernet)
           RX packets 50  bytes 6690 (6.5 KiB)
           RX errors 0  dropped 0  overruns 0  frame 0
           TX packets 67  bytes 11488 (11.2 KiB)
           TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
   

   Schedule: biosdevname and net.ifnames parameters:

   Name card	biosname	net.ifnames
   ens33(default)	0	0
   em1	1	0
   eth0	0	0

   Note: Some Tips modify the network card with file NAME parameter is eth0not required and only need to add biosdevname net.ifnames parameters can be configured for this purpose in the grub

1.1.4 View Card physical connection (ie 网线连接状态):mii-tool

2. Network configuration: / etc / sysconfig / network-script /

2.1 modify the network card configuration

• ifconfig <Interface Interface> <IP address> [netmask] # modify IP network interface
• ifup <Interface Interface> # Enable Network Interface
• ifdown <Interface Interface> # Disable Network Interface

2.2 network control command: ipCommand VS sscommand

• ip addr # View card information
  • ifconfig
• ip link set dev eth0 up # Enable NIC
  • ifup eth0
• ip addr add 192.168.5.130/24 dev eth0 # add an address to the network card
  • ifconfig eth0 192.168.5.130 netmask 255.255.255.0
• ip route add 192.168.6 / 24 via 192.168.0.1 # added Gateway
  • route add -net 192.168.6.0 netmask 255.255.255.0 gw 192.168.0.1

3. Route command: ip route

View the routing information:

[root@localhost ~]# ip route show|column -t
default           via  192.168.5.2  dev    eth0
default           via  192.168.5.2  dev    eth0    proto  dhcp  metric  100
192.168.5.0/24    dev  eth0         proto  kernel  scope  link  src     192.168.5.128  metric  100
192.168.122.0/24  dev  virbr0       proto  kernel  scope  link  src     192.168.122.1

4. Network troubleshooting

• Network connectivity ping #
• traceroute # routing status
• mtr # packet loss state
• DNS dig nslookup #
• tcpdump # crawl the web Package
• netstat # View application port status
• ss # View application port status ( recommended )

  [root@localhost ~]# ss -ntpl |column -t 
  State   Recv-Q  Send-Q  Local             Address:Port  Peer                                                       Address:Port
  LISTEN  0       128     *:111             *:*           users:(("rpcbind",pid=6174,fd=4),("systemd",pid=1,fd=49))
  LISTEN  0       5       192.168.122.1:53  *:*           users:(("dnsmasq",pid=7165,fd=6))
  LISTEN  0       128     *:22              *:*           users:(("sshd",pid=6773,fd=3))
  LISTEN  0       128     127.0.0.1:631     *:*           users:(("cupsd",pid=6774,fd=12))
  LISTEN  0       100     127.0.0.1:25      *:*           users:(("master",pid=7176,fd=13))
  LISTEN  0       128     127.0.0.1:6010    *:*           users:(("sshd",pid=6857,fd=9))
  LISTEN  0       128     :::111            :::*          users:(("rpcbind",pid=6174,fd=6),("systemd",pid=1,fd=51))
  LISTEN  0       128     :::22             :::*          users:(("sshd",pid=6773,fd=4))
  LISTEN  0       128     ::1:631           :::*          users:(("cupsd",pid=6774,fd=11))
  LISTEN  0       100     ::1:25            :::*          users:(("master",pid=7176,fd=14))
  LISTEN  0       128     ::1:6010          :::*          users:(("sshd",pid=6857,fd=8))
  

5. Web Services Management: network