Linux_网络基础管理

一、网卡的命名

1、传统网卡命名

eth0、eth1、eth2、eth3.........
wlan0、wlan1、waln2、wlan3.........

2、RHEL7命名机制

systemd对网络设备的命名方式：
- 如果firmware或BIOS为主板上集成的设备提供的索引信息可用，且可预测，则根据此索引进行命名，例如：eno1
- 如果firmware或BIOS为PCI-E扩展槽所提供的索引信息可用，且可预测，则根据此索引进行命名，例如：ens1
- 如果硬件接口的物理位置信息可用，则根据此信息进行命名，例如：enp2s0
- 如果用户显式启动，也可根据MAC地址进行命名，例如：enx2387a1dc56
- 上述均不可用时，则使用传统命名机制
上述命名机制中，有的需要biosdevname程序的参与，所以必须安装biosdevname程序且启用它。

3、网卡接口名称组成

基于固件、设备结构、设备类型三种方式：
- 由两个字母开头标示固件
  - 以太网网卡以 en开头
  - 无线网卡以wl开头
- 设备结构
  - o：主板上集成的设备的设备索引号
  - s：扩展槽的索引号
  - x：基于MAC地址的命名
  - p<bus>s<slot>：基于物理位置拓扑的命名。如：enp2s1，表示PCI总线上第2个总线的第1个插槽的设备索引号

4、重设传统网卡命名

修改网卡配置文件

//修改网卡配置文件
[root@localhost ~]# cd /etc/sysconfig/network-scripts/
[root@localhost network-scripts]# ls
ifcfg-ens160
[root@localhost network-scripts]# mv ifcfg-ens160 ifcfg-eth0
[root@localhost network-scripts]# ls
ifcfg-eth0
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=eth0        //把ens160换成eth0
UUID=cf57c3f1-7eaf-489c-86d4-2ebbc39f6105
DEVICE=eth0     //把ens160换成eth0
ONBOOT=yes

编辑/etc/default/grub配置文件，在以GRUB_CMDLINE_LINUX开头的行内rhgb的前面加上net.ifnames=0 biosdevname=0

[root@localhost ~]# vim /etc/default/grub 
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap net.ifnames=0 biosdevname=0 rhgb quiet"
GRUB_DISABLE_RECOVERY="true"
GRUB_ENABLE_BLSCFG=true

为grub2生成配置文件

 //为grub2生成配置文件
[root@localhost ~]# grub2-mkconfig -o /etc/grub2.cfg  （-o:outpu更新配置文件更新到/etc/grub2.cfg）
Generating grub configuration file ...
done
[root@localhost ~]# reboot 
 //生成配置文件后需要重启

查看网卡名称

//之前的网卡名称
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens160: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:cd:6a:1b brd ff:ff:ff:ff:ff:ff
    inet 192.168.174.128/24 brd 192.168.174.255 scope global dynamic noprefixroute ens160
       valid_lft 1750sec preferred_lft 1750sec
    inet6 fe80::dc83:4685:5028:2c09/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

//重设网卡名之后
[root@localhost ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:cd:6a:1b brd ff:ff:ff:ff:ff:ff
    inet 192.168.174.128/24 brd 192.168.174.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::6cda:49cd:383e:cfa3/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

二、网络管理常用的命令

1、ifconfig命令（用于查看当前处于活跃状态的网络接口）

ifconfig —— 命令

[root@localhost ~]# ifconfig 
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.174.128  netmask 255.255.255.0  broadcast 192.168.174.255
        inet6 fe80::6cda:49cd:383e:cfa3  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:cd:6a:1b  txqueuelen 1000  (Ethernet)
        RX packets 95  bytes 9605 (9.3 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 93  bytes 10685 (10.4 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 12  bytes 1020 (1020.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12  bytes 1020 (1020.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

仅查看eth0网卡的状态信息

[root@localhost ~]# ifconfig eth0
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.174.128  netmask 255.255.255.0  broadcast 192.168.174.255
        inet6 fe80::6cda:49cd:383e:cfa3  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:cd:6a:1b  txqueuelen 1000  (Ethernet)
        RX packets 111  bytes 10847 (10.5 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 108  bytes 12827 (12.5 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

查看所以网卡状态信息（包括禁用和启用的）

[root@localhost ~]# ifconfig -a
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.174.128  netmask 255.255.255.0  broadcast 192.168.174.255
        inet6 fe80::6cda:49cd:383e:cfa3  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:cd:6a:1b  txqueuelen 1000  (Ethernet)
        RX packets 134  bytes 12673 (12.3 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 124  bytes 14771 (14.4 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 12  bytes 1020 (1020.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12  bytes 1020 (1020.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

网卡配置信息含义

UP：   网卡处于活动状态
BROADCAST： 支持广播
RUNNING：   网线已接入
MULTICAST： 支持组播
MTU：  最大传输单元(字节) ,即此接口一次所能传输的最大封包

inet：  显示IPv4地址行
inet6： 显示IPv6地址行
link/enther： 指设备硬件(MAC )地址
txqueuelen：  传输缓存区长度大小
RX packets：  接收的数据包
TX packets：  发送的数据包
errors：  总的收包的错误数量
dropped： 由于各种原因，导致拷贝在内存过程中被丢弃
collisions：  网络信号冲突情况，值不为0则可能存在网络故障

2、ip —— 命令

语法：

ip [ option ] object { command  | help }
object :
      link：网络接口
      addr：协议地址
      route：路由

查看网络接口所有地址

[root@localhost ~]# ip link show 
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether 00:0c:29:cd:6a:1b brd ff:ff:ff:ff:ff:ff

显示报文统计信息

[root@localhost ~]# ip -s link show 
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    RX: bytes  packets  errors  dropped overrun mcast   
    1020       12       0       0       0       0       
    TX: bytes  packets  errors  dropped carrier collsns 
    1020       12       0       0       0       0       
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether 00:0c:29:cd:6a:1b brd ff:ff:ff:ff:ff:ff
    RX: bytes  packets  errors  dropped overrun mcast   
    21460      245      0       0       0       0       
    TX: bytes  packets  errors  dropped carrier collsns 
    21963      202      0       0       0       0

启用或禁用网络接口

语法：ip link set devname ｛ up | down｝ 

[root@localhost ~]# ip link set lo down 
[root@localhost ~]# ip link set lo up

添加ip地址

语法：ip addr add ip/prefix dev devname

[root@localhost ~]# ip addr show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:cd:6a:1b brd ff:ff:ff:ff:ff:ff
    inet 192.168.174.128/24 brd 192.168.174.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::6cda:49cd:383e:cfa3/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
[root@localhost ~]# ip addr add 192.168.174.150/24 dev eth0 
[root@localhost ~]# ip addr show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:cd:6a:1b brd ff:ff:ff:ff:ff:ff
    inet 192.168.174.128/24 brd 192.168.174.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet 192.168.174.150/24 scope global secondary eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::6cda:49cd:383e:cfa3/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

删除ip地址

语法：ip addr del ip/prefix dev devname

[root@localhost ~]# ip addr show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:cd:6a:1b brd ff:ff:ff:ff:ff:ff
    inet 192.168.174.128/24 brd 192.168.174.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet 192.168.174.150/24 scope global secondary eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::6cda:49cd:383e:cfa3/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever
[root@localhost ~]# ip addr del 192.168.174.150/24 dev eth0 
[root@localhost ~]# ip addr show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:cd:6a:1b brd ff:ff:ff:ff:ff:ff
    inet 192.168.174.128/24 brd 192.168.174.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::6cda:49cd:383e:cfa3/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

查看网络接口地址

语法：ip addr show devname

[root@localhost ~]# ip addr show 
[root@localhost ~]# ip addr show eth0 
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 00:0c:29:cd:6a:1b brd ff:ff:ff:ff:ff:ff
    inet 192.168.174.128/24 brd 192.168.174.255 scope global noprefixroute eth0
       valid_lft forever preferred_lft forever
    inet6 fe80::6cda:49cd:383e:cfa3/64 scope link noprefixroute 
       valid_lft forever preferred_lft forever

3、route —— 命令

Linux主机之间是使用IP进行通信，假设A主机和B主机同在一个网段内且网卡都处于激活状态，则A具备和B直接通信的能力，但如果A主机和B主机处于两个不同的网段，则A必须通过路由器才能和B通信，路由器属于IT设备的基础设施，每个网段都应该至少有一个网关

查看当前路由表（有的默认安装了route命令；最小化安装的没有route命令，需要手动安装net-tools安装包）

[root@localhost ~]# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         _gateway        0.0.0.0         UG    100    0        0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U     100    0        0 eth0

以数字方式显示各主机或端口等相关信息

[root@localhost ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.174.2   0.0.0.0         UG    100    0        0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U     100    0        0 eth0

增加路由

语法：route add  [ net | host ] ip/prefix gw dev devname  （net：主机路由；host：主机路由）

[root@localhost ~]# route add -net 192.168.1.0/24 gw 192.168.174.2 dev eth0 
[root@localhost ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.174.2   0.0.0.0         UG    100    0        0 eth0
192.168.1.0     192.168.174.2   255.255.255.0   UG    0      0        0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U     100    0        0 eth0
[root@localhost ~]# route add -net 0.0.0.0/0 gw 192.168.174.2 dev eth0
[root@localhost ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.174.2   0.0.0.0         UG    0      0        0 eth0
0.0.0.0         192.168.174.2   0.0.0.0         UG    100    0        0 eth0   (这条路由条目是原本就有的)
192.168.1.0     192.168.174.2   255.255.255.0   UG    0      0        0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U     100    0        0 eth0

增加主机路由

[root@localhost ~]# route add -host 192.168.174.150 gw 192.168.174.2
[root@localhost ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.174.2   0.0.0.0         UG    100    0        0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U     100    0        0 eth0
192.168.174.150 192.168.174.2   255.255.255.255 UGH   0      0        0 eth0

[root@localhost ~]# route del -host 192.168.174.150
[root@localhost ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.174.2   0.0.0.0         UG    100    0        0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U     100    0        0 eth0

三、网路相关配置文件

1、网络配置文件

网络配置文件：/etc/sysconfig/network
NETWORKING= [ yes | no ]：设置整个系统是否启用网络功能，若设为no，则无论网卡如何设置都不难使用网络功能
HOSTNAME：设置主机名

2、网卡接口配置文件

网卡接口的配置文件路径：/etc/sysconfig/network-scripts/ifcfg-devname

[root@localhost ~]# vim /etc/sysconfig/network-scripts/ifcfg-eth0 
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
NAME=eth0
UUID=cf57c3f1-7eaf-489c-86d4-2ebbc39f6105
DEVICE=eth0
ONBOOT=yes

3、网卡配置说明

BOOTPROTO=none       //引导协议，可选值有{static /none / dhcp /bootp}
NM_ CONTROLLED       //NM是NetworkManager的简写，可选值有{yes/no}
TYPE            //接口类型；常见的接口类型有: Etherdet, Bridge
UUID           //设备的惟一标识
HWADDR      //硬件地址，要与硬件中的地址保持一-致，可省
IPADDR=172.16.12.130    //固定IP地址
PREFIX=24         //子网掩码
NETMASK=255.255.255.0        //子网掩码
GATEWAY=172.16.12.2           //默认网关
DNS1=172.16.12.2                 //第一个DNS服务器指向
DNS2                      //第二个DNS服务器指向
DNS3                 //第三个DNS服务器指向
DEVICE=eth1         //关联的设备名称，要与文件名的后半部INTERFACE_ NAME"保持一致
NAME="eth1"          //连接名称
ONB00T=yes            //在系统引导时是否自动激活此网络接口，可选值有{ yes / no }
DEFROUTE=yes         //将接口设定为默认路由｛ yes |no }
USERCTL={yes |no}      //是否允许普通用户控制此接口的启用与禁用
PEERDNS={yes |no}       //是否在BOOTPROTO为dhcp时接受由dhcp服务器指定的DNS地址

4、路由配置文件

配置文件路径

/etc/sysconfig/network-scripts/route-eth0（route-网卡设备名称）

添加路由方式一：（方式一是最常用的、最简单明了、个人推荐的使用的方法；其中via指的是下一跳）

[root@localhost ~]# cd /etc/sysconfig/network-scripts/
[root@localhost network-scripts]# vim route-eth0
192.168.11.0/24 via 192.168.174.2
192.168.12.0/24 via 192.168.174.2
192.168.13.0/24 via 192.168.174.2
[root@localhost network-scripts]# ifdown eth0;ifup eth0 
成功停用连接 "eth0"（D-Bus 活动路径：/org/freedesktop/NetworkManager/ActiveConnection/19）

连接已成功激活（D-Bus 活动路径：/org/freedesktop/NetworkManager/ActiveConnection/21）
[root@localhost network-scripts]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.11.0    192.168.174.2   255.255.255.0   UG    100    0        0 eth0
192.168.12.0    192.168.174.2   255.255.255.0   UG    100    0        0 eth0
192.168.13.0    192.168.174.2   255.255.255.0   UG    100    0        0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U     100    0        0 eth0

添加路由方式二：（方式二相对方式一比较麻烦，个人不推荐使用方式二）

[root@localhost ~]# cd /etc/sysconfig/network-scripts/
[root@localhost network-scripts]# vim route-eth0 
ADDRESS0=192.168.1.0
NETMASK0=255.255.255.0
GATEWAY0=192.168.174.2

ADDRESS1=192.168.2.0
NETMASK1=255.255.255.0
GATEWAY1=192.168.174.2
[root@localhost network-scripts]# ifdown eth0;ifup eth0 
成功停用连接 "eth0"（D-Bus 活动路径：/org/freedesktop/NetworkManager/ActiveConnection/17）

连接已成功激活（D-Bus 活动路径：/org/freedesktop/NetworkManager/ActiveConnection/19）
[root@localhost network-scripts]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.0     192.168.174.2   255.255.255.0   UG    100    0        0 eth0
192.168.2.0     192.168.174.2   255.255.255.0   UG    100    0        0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U     100    0        0 eth0

添加到主机的路由：（添加到主机指的是只能与该主机通信）

[root@localhost ~]# cd /etc/sysconfig/network-scripts/
[root@localhost network-scripts]# vim route-eth0
192.168.1.1/32 via 192.168.174.2
192.168.2.2/32 via 192.168.174.2
192.168.3.3/32 via 192.168.174.2
[root@localhost network-scripts]# ifdown eth0;ifup eth0 
成功停用连接 "eth0"（D-Bus 活动路径：/org/freedesktop/NetworkManager/ActiveConnection/21）

连接已成功激活（D-Bus 活动路径：/org/freedesktop/NetworkManager/ActiveConnection/23）
[root@localhost network-scripts]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.1.1     192.168.174.2   255.255.255.255 UGH   100    0        0 eth0
192.168.2.2     192.168.174.2   255.255.255.255 UGH   100    0        0 eth0
192.168.3.3     192.168.174.2   255.255.255.255 UGH   100    0        0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U     100    0        0 eth0

5、DNS配置文件

DNS配置文件路径

/etc/resolv.conf

查看配置文件

[root@localhost ~]# vim /etc/resolv.conf 
# Generated by NetworkManager
nameserver 8.8.8.8

 //查看网卡的dns
[root@localhost ~]# vim /etc/sysconfig/network-scripts/ifcfg-eth0
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
NAME=eth0
UUID=cf57c3f1-7eaf-489c-86d4-2ebbc39f6105
DEVICE=eth0
ONBOOT=yes
DNS1=8.8.8.8
IPADDR=192.168.174.128
PREFIX=24
 //只需更改网卡里面的的DNS，不需要更改/etc/resolv.conf里面的内容

四、NetworkManager管理网络

1、NetworkManager基本概念

1️⃣：RHEL/CentOS7系统默认使用NetworkManager来提供网络服务，这是一种动态管理网络配置的守护进程，能够让网络设备保持连接状态。

2️⃣：NetworkManager提供的命令行和图形配置工具对网络进行设定，设定保存的配置文件。

3️⃣：在/etc/sysconf ig/network-scripts目录下，工具有nmcli, nmtui, nm- connect ion-editor

4️⃣：device物理设备,例如ens33 , enp2s0, virbr0, team0

5️⃣：connection连接设置，具体网络配置方案：

不同的网络连接配置可以应用到相同的物理设备，但物理设备同一时间只能应用其中某个网络连接

针对物理网络接口，设定不同的网络连接,在不同的使用环境中激活相应的网络连接，就可以实现网络配置信息的自动切换了

2、查看NetworkManager状态：

[root@localhost ~]# systemctl status NetworkManager
● NetworkManager.service - Network Manager
   Loaded: loaded (/usr/lib/systemd/system/NetworkManager.service; enabled; vendor preset: enabled)
   Active: active (running) since Tue 2020-08-18 05:32:03 CST; 38min ago
     Docs: man:NetworkManager(8)
 Main PID: 5188 (NetworkManager)
    Tasks: 3 (limit: 12356)
   Memory: 4.4M
   CGroup: /system.slice/NetworkManager.service
           └─5188 /usr/sbin/NetworkManager --no-daemon

8月 18 05:58:40 localhost.localdomain NetworkManager[5188]: <info>  [1597701520.3406] device (eth0): Activation: starting connection 'eth0' (cf57c3f1-7eaf-489c-86d4-2ebbc39f6105)
8月 18 05:58:40 localhost.localdomain NetworkManager[5188]: <info>  [1597701520.3422] device (eth0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed')
8月 18 05:58:40 localhost.localdomain NetworkManager[5188]: <info>  [1597701520.3425] manager: NetworkManager state is now CONNECTING
8月 18 05:58:40 localhost.localdomain NetworkManager[5188]: <info>  [1597701520.3427] device (eth0): state change: prepare -> config (reason 'none', sys-iface-state: 'managed')
8月 18 05:58:40 localhost.localdomain NetworkManager[5188]: <info>  [1597701520.3433] device (eth0): state change: config -> ip-config (reason 'none', sys-iface-state: 'managed')
8月 18 05:58:40 localhost.localdomain NetworkManager[5188]: <info>  [1597701520.3456] device (eth0): state change: ip-config -> ip-check (reason 'none', sys-iface-state: 'managed')
8月 18 05:58:40 localhost.localdomain NetworkManager[5188]: <info>  [1597701520.3593] device (eth0): state change: ip-check -> secondaries (reason 'none', sys-iface-state: 'managed')
8月 18 05:58:40 localhost.localdomain NetworkManager[5188]: <info>  [1597701520.3596] device (eth0): state change: secondaries -> activated (reason 'none', sys-iface-state: 'managed')
8月 18 05:58:40 localhost.localdomain NetworkManager[5188]: <info>  [1597701520.3599] manager: NetworkManager state is now CONNECTED_LOCAL
8月 18 05:58:40 localhost.localdomain NetworkManager[5188]: <info>  [1597701520.3669] device (eth0): Activation: successful, device activated.

3、使用nmcli命令查看设备以及连接状态

查看设备状态

[root@localhost ~]# nmcli device
DEVICE  TYPE      STATE   CONNECTION 
eth0    ethernet  已连接  eth0       
lo      loopback  未托管  --

查看所有网卡设备信息

[root@localhost ~]# nmcli device show 
GENERAL.DEVICE:                         eth0
GENERAL.TYPE:                           ethernet
GENERAL.HWADDR:                         00:0C:29:CD:6A:1B
GENERAL.MTU:                            1500
GENERAL.STATE:                          100（已连接）
GENERAL.CONNECTION:                     eth0
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveConnection/25
WIRED-PROPERTIES.CARRIER:               开
IP4.ADDRESS[1]:                         192.168.174.128/24
IP4.GATEWAY:                            --
IP4.ROUTE[1]:                           dst = 192.168.174.0/24, nh = 0.0.0.0, mt = 100
IP4.ROUTE[2]:                           dst = 192.168.1.1/32, nh = 192.168.174.2, mt = 100
IP4.ROUTE[3]:                           dst = 192.168.2.2/32, nh = 192.168.174.2, mt = 100
IP4.ROUTE[4]:                           dst = 192.168.3.3/32, nh = 192.168.174.2, mt = 100
IP4.DNS[1]:                             8.8.8.8
IP6.ADDRESS[1]:                         fe80::6cda:49cd:383e:cfa3/64
IP6.GATEWAY:                            --
IP6.ROUTE[1]:                           dst = fe80::/64, nh = ::, mt = 100
IP6.ROUTE[2]:                           dst = ff00::/8, nh = ::, mt = 256, table=255

GENERAL.DEVICE:                         lo
GENERAL.TYPE:                           loopback
GENERAL.HWADDR:                         00:00:00:00:00:00
GENERAL.MTU:                            65536
GENERAL.STATE:                          10（未托管）
GENERAL.CONNECTION:                     --
GENERAL.CON-PATH:                       --
IP4.ADDRESS[1]:                         127.0.0.1/8
IP4.GATEWAY:                            --
IP6.ADDRESS[1]:                         ::1/128
IP6.GATEWAY:                            --

查看指定设备信息

[root@localhost ~]# nmcli device show eth0 
GENERAL.DEVICE:                         eth0
GENERAL.TYPE:                           ethernet
GENERAL.HWADDR:                         00:0C:29:CD:6A:1B
GENERAL.MTU:                            1500
GENERAL.STATE:                          100（已连接）
GENERAL.CONNECTION:                     eth0
GENERAL.CON-PATH:                       /org/freedesktop/NetworkManager/ActiveConnection/25
WIRED-PROPERTIES.CARRIER:               开
IP4.ADDRESS[1]:                         192.168.174.128/24
IP4.GATEWAY:                            --
IP4.ROUTE[1]:                           dst = 192.168.174.0/24, nh = 0.0.0.0, mt = 100
IP4.ROUTE[2]:                           dst = 192.168.1.1/32, nh = 192.168.174.2, mt = 100
IP4.ROUTE[3]:                           dst = 192.168.2.2/32, nh = 192.168.174.2, mt = 100
IP4.ROUTE[4]:                           dst = 192.168.3.3/32, nh = 192.168.174.2, mt = 100
IP4.DNS[1]:                             8.8.8.8
IP6.ADDRESS[1]:                         fe80::6cda:49cd:383e:cfa3/64
IP6.GATEWAY:                            --
IP6.ROUTE[1]:                           dst = fe80::/64, nh = ::, mt = 100
IP6.ROUTE[2]:                           dst = ff00::/8, nh = ::, mt = 256, table=255

查看网卡连接状态

[root@localhost ~]# nmcli connection 
NAME        UUID                                  TYPE      DEVICE 
eth0        cf57c3f1-7eaf-489c-86d4-2ebbc39f6105  ethernet  eth0   
有线连接 1  a026ad4d-b586-32c4-908a-0501f9f2b522  ethernet  --

查看指定网卡连接信息

[root@localhost ~]# nmcli connection show eth0 
connection.id:                          eth0
connection.uuid:                        cf57c3f1-7eaf-489c-86d4-2ebbc39f6105
connection.stable-id:                   --
connection.type:                        802-3-ethernet
connection.interface-name:              eth0
connection.autoconnect:                 是
connection.autoconnect-priority:        0
connection.autoconnect-retries:         -1 (default)
connection.multi-connect:               0（default）
connection.auth-retries:                -1
connection.timestamp:                   1597702924
connection.read-only:                   否
connection.permissions:                 --
connection.zone:                        --
connection.master:                      --
connection.slave-type:                  --
connection.autoconnect-slaves:          -1（default）
...........

五、网络管理常用命令

1、ping —— 命令

目的：测试另一台主机是否可达，如果ping不到某台主机，就说明对方主机以及出现了问题，但不排除由于防火墙的原因、ICMP包被丢弃等原因造成ping不通的情况。
常用命令：

ping命令常用选项：
    -c ：指定ping包的次数
    -i ：指定ping包发送间隔
    -w ：如果pingh'm没有回应。则在指定超时后退出

实例：

 //指定ping包次数
[root@localhost ~]# ping -c 3 www.baidu.com
PING www.a.shifen.com (14.215.177.38) 56(84) bytes of data.
64 bytes from 14.215.177.38 (14.215.177.38): icmp_seq=1 ttl=128 time=25.10 ms
64 bytes from 14.215.177.38 (14.215.177.38): icmp_seq=2 ttl=128 time=25.4 ms
64 bytes from 14.215.177.38 (14.215.177.38): icmp_seq=3 ttl=128 time=23.3 ms

--- www.a.shifen.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 5ms
rtt min/avg/max/mdev = 23.331/24.910/25.977/1.154 ms

 //指定ping包的时间间隔
[root@localhost ~]# ping -i 2 -c 3 www.baidu.com
PING www.a.shifen.com (14.215.177.38) 56(84) bytes of data.
64 bytes from 14.215.177.38 (14.215.177.38): icmp_seq=1 ttl=128 time=23.8 ms
64 bytes from 14.215.177.38 (14.215.177.38): icmp_seq=2 ttl=128 time=24.8 ms
64 bytes from 14.215.177.38 (14.215.177.38): icmp_seq=3 ttl=128 time=21.9 ms

--- www.a.shifen.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 10ms
rtt min/avg/max/mdev = 21.906/23.477/24.759/1.182 ms

2、host命令和nslookup命令

作用：host和nslookup命令都是用于查询DNS记录的
实例：

[root@localhost ~]# host www.baidu.com
www.baidu.com is an alias for www.a.shifen.com.
www.a.shifen.com has address 14.215.177.38
www.a.shifen.com has address 14.215.177.39

[root@localhost ~]# nslookup www.baidu.com
Server:		192.168.174.2
Address:	192.168.174.2#53

Non-authoritative answer:
www.baidu.com	canonical name = www.a.shifen.com.
Name:	www.a.shifen.com
Address: 14.215.177.39
Name:	www.a.shifen.com
Address: 14.215.177.38

3、netstat命令（查看网络状态；最小化安装默认是没有装netstat命令，需要手动安装net-tools安装包）

查看路由表

[root@localhost ~]# netstat -r
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
default         _gateway        0.0.0.0         UG        0 0          0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U         0 0          0 eth0

以数字方式显示路由表

[root@localhost ~]# netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.174.2   0.0.0.0         UG        0 0          0 eth0
192.168.174.0   0.0.0.0         255.255.255.0   U         0 0          0 eth0

查看所以状态连接

[root@localhost ~]# netstat -a
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State      
tcp        0      0 0.0.0.0:ssh             0.0.0.0:*               LISTEN     
tcp        0      0 localhost.localdoma:ssh 192.168.174.1:9531      ESTABLISHED
tcp        0      0 localhost.localdoma:ssh 192.168.174.1:12204     ESTABLISHED
tcp        0    208 localhost.localdoma:ssh 192.168.174.1:4293      ESTABLISHED
tcp6       0      0 [::]:ssh                [::]:*                  LISTEN     
raw6       0      0 [::]:ipv6-icmp          [::]:*                  7          
Active UNIX domain sockets (servers and established)
..........

显示监听指定的套接字的进程号及进程名

[root@localhost ~]# netstat -p
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 localhost.localdoma:ssh 192.168.174.1:9531      ESTABLISHED 1220/sshd: root [pr 
tcp        0      0 localhost.localdoma:ssh 192.168.174.1:12204     ESTABLISHED 1412/sshd: root [pr 
tcp        0     36 localhost.localdoma:ssh 192.168.174.1:4293      ESTABLISHED 5011/sshd: root [pr 
Active UNIX domain sockets (w/o servers)
............

常用选项：-antlp

[root@localhost ~]# netstat -antlp
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      1010/sshd           
tcp        0      0 192.168.174.128:22      192.168.174.1:9531      ESTABLISHED 1220/sshd: root [pr 
tcp        0      0 192.168.174.128:22      192.168.174.1:12204     ESTABLISHED 1412/sshd: root [pr 
tcp        0     36 192.168.174.128:22      192.168.174.1:4293      ESTABLISHED 5011/sshd: root [pr 
tcp6       0      0 :::22                   :::*                    LISTEN      1010/sshd

4、ss命令（网络状态查看工具，与netstat命令差不多）

语法：ss [ option ] [ FILTER ]
常用的选项：

options:
    -t: tcp协议相关-u: udp协议相关-W:裸套接字相关-x: unix套接字相关-l: listen状态的连接-a:所有
    -n：数字格式
    -p：相关的程序及pid-e:扩展的信息
    -m：内存用量
    -0：显示计时器信息

常见的FILTER

FILTERs:
FILTER := [ state TCP-STATE] [ EXPRESSION ]
如: ss -antlp state ESTABLISHED

实例：

[root@localhost ~]# ss -antlp 
State             Recv-Q             Send-Q                          Local Address:Port                           Peer Address:Port                                                         
LISTEN            0                  128                                   0.0.0.0:22                                  0.0.0.0:*                 users:(("sshd",pid=1010,fd=4))             
LISTEN            0                  128                                      [::]:22                                     [::]:*                 users:(("sshd",pid=1010,fd=6)) 

[root@localhost ~]# ss -antlp state ESTABLISHED
Recv-Q           Send-Q                          Local Address:Port                         Peer Address:Port                                                                               
0                0                             192.168.174.128:22                          192.168.174.1:9531              users:(("sshd",pid=1233,fd=5),("sshd",pid=1220,fd=5))            
0                0                             192.168.174.128:22                          192.168.174.1:12204             users:(("sshd",pid=1414,fd=5),("sshd",pid=1412,fd=5))            
0                36                            192.168.174.128:22                          192.168.174.1:4293              users:(("sshd",pid=5013,fd=5),("sshd",pid=5011,fd=5))

常见的state：

常见的state:
tcp finite state machine: 有限状态机
    LISTENING:监听
    ESTABLISHED:已建立的连接
EXPRESSION:
dport =
sport =

示例: '( dport = :ssh or sport = :ssh)'，此处的ssh也即服务名可以使用其对应的端口号代替

实例：

[root@localhost ~]# ss -antlp state ESTABLISHED '( dport = :ssh or sport = :ssh )'
Recv-Q           Send-Q                          Local Address:Port                         Peer Address:Port                                                                               
0                0                             192.168.174.128:22                          192.168.174.1:9531              users:(("sshd",pid=1233,fd=5),("sshd",pid=1220,fd=5))            
0                0                             192.168.174.128:22                          192.168.174.1:12204             users:(("sshd",pid=1414,fd=5),("sshd",pid=1412,fd=5))            
0                36                            192.168.174.128:22                          192.168.174.1:4293              users:(("sshd",pid=5013,fd=5),("sshd",pid=5011,fd=5))

常见端口：

http     80/tcp
httpd    443/tcp
ssh      22/tcp
ftp      20,21/tcp
mysql    3306/tc[
rsync    873/rsync
redis    6379/tcp

Windows远程：3389/tcp
dhcp      67/tcp
dns       53/tcp
MSSQL     1433/tcp
tomcat    8080
postfix    25