一、nmtui手工添加IP
看一下当前网络设备的IP，为了精简指令输出，指令就要复杂一些了：
[root@CentOS7 ~]# nmcli -t -f IP4.ADDRESS dev show enp0s3
IP4.ADDRESS[1]:ip = 192.168.150.110/24, gw = 192.168.150.254
[root@centos7 ~]#
[root@centos7 ~]# ip addr show enp0s3 scope global
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 08:00:27:15:35:d2 brd ff:ff:ff:ff:ff:ff
inet 192.168.150.110/24 brd 192.168.150.255 scope global enp0s3
valid_lft forever preferred_lft forever
[root@centos7 ~]#
[root@centos7 ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
......
IPADDR0=192.168.150.110
PREFIX0=24
GATEWAY0=192.168.150.254
DNS1=192.168.150.254
HWADDR=08:00:27:15:35:D2
IPADDR1=192.168.150.111
PREFIX1=24
[root@centos7 ~]#
新IP已经被加入到ifcfg-eth0中，原始地址的关键字是 IPADDR0、PREFIX0，新地址的关键字是 IPADDR1、PREFIX1 。
[root@centos7 ~]# nmcli con load /etc/sysconfig/network-scripts/ifcfg-eth0
[root@centos7 ~]#
[root@centos7 ~]# nmcli -t -f IP4.ADDRESS dev show enp0s3
IP4.ADDRESS[1]:ip = 192.168.150.110/24, gw = 192.168.150.254
[root@centos7 ~]#
[root@centos7 ~]# ip addr show enp0s3 scope global
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 08:00:27:15:35:d2 brd ff:ff:ff:ff:ff:ff
inet 192.168.150.110/24 brd 192.168.150.255 scope global enp0s3
valid_lft forever preferred_lft forever
[root@centos7 ~]#
load connection 后，NetworkManager 也没有知晓新增IP，新增IP也没有出现在 ip addr show 中。
[root@centos7 ~]# systemctl restart network
[root@centos7 ~]#
[root@centos7 ~]# nmcli -t -f IP4.ADDRESS dev show enp0s3
IP4.ADDRESS[1]:ip = 192.168.150.110/24, gw = 192.168.150.254
IP4.ADDRESS[2]:ip = 192.168.150.111/24, gw = 192.168.150.254
[root@centos7 ~]#
[root@centos7 ~]# ip addr show enp0s3 scope global
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 08:00:27:15:35:d2 brd ff:ff:ff:ff:ff:ff
inet 192.168.150.110/24 brd 192.168.150.255 scope global enp0s3
valid_lft forever preferred_lft forever
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# ping 192.168.150.111
PING 192.168.150.111 (192.168.150.111) 56(84) bytes of data.
From 192.168.150.110 icmp_seq=1 Destination Host Unreachable
From 192.168.150.110 icmp_seq=2 Destination Host Unreachable
......
[root@centos7 ~]#
重启network服务后，NetworkManager 知晓新增IP了，但新增IP还是没有生效。
[root@centos7 ~]# nmcli dev connect enp0s3
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# nmcli -t -f IP4.ADDRESS dev show enp0s3
IP4.ADDRESS[1]:ip = 192.168.150.110/24, gw = 192.168.150.254
IP4.ADDRESS[2]:ip = 192.168.150.111/24, gw = 192.168.150.254
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# ip addr show enp0s3 scope global
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 08:00:27:15:35:d2 brd ff:ff:ff:ff:ff:ff
inet 192.168.150.110/24 brd 192.168.150.255 scope global enp0s3
valid_lft forever preferred_lft forever
inet 192.168.150.111/24 brd 192.168.150.255 scope global secondary enp0s3
valid_lft forever preferred_lft forever
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# ping 192.168.150.111
PING 192.168.150.111 (192.168.150.111) 56(84) bytes of data.
64 bytes from 192.168.150.111: icmp_seq=1 ttl=64 time=0.039 ms
64 bytes from 192.168.150.111: icmp_seq=2 ttl=64 time=0.079 ms
......
[root@centos7 ~]#
重新连接设备 enp0s3，新IP生效了。注意：不需要先断开设备（nmcli dev disconnect enp0s3），断开设备的话ssh立刻断线。重新连接设备的过程中，ssh是不会断线的。
nmtui添加IP后，需要：
nmcli con load /etc/sysconfig/network-scripts/ifcfg-eth0
nmcli dev connect enp0s3
二、手工添加IP到ifcfg-eth0
在ifcfg-eth0配置文件中手工添加如下两行：
IPADDR2=192.168.150.112
PREFIX2=24
先执行 nmcli con load /etc/sysconfig/network-scripts/ifcfg-eth0 后，在nmtui中可以看到新增IP。（也可以简单的用 nmcli con reload ，reload 和 load的区别自己脑补一下吧。）
再执行 nmcli dev connect enp0s3 后，IP 192.168.150.112 才生效的。
手工添加IP到ifcfg-eth0后，需要：
nmcli con load /etc/sysconfig/network-scripts/ifcfg-eth0 或 nmcli con reload
nmcli dev connect enp0s3
三、用ip addr add指令添加/删除IP，即刻生效，重启不保留。
在线添加IP：
[root@centos7 ~]# ip addr add 192.168.150.113/24 dev enp0s3
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# nmcli -t -f IP4.ADDRESS dev show enp0s3
IP4.ADDRESS[1]:ip = 192.168.150.110/24, gw = 192.168.150.254
IP4.ADDRESS[2]:ip = 192.168.150.111/24, gw = 192.168.150.254
IP4.ADDRESS[3]:ip = 192.168.150.112/24, gw = 192.168.150.254
IP4.ADDRESS[4]:ip = 192.168.150.113/24, gw = 192.168.150.254
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# ip addr show enp0s3 scope global
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 08:00:27:15:35:d2 brd ff:ff:ff:ff:ff:ff
inet 192.168.150.110/24 brd 192.168.150.255 scope global enp0s3
valid_lft forever preferred_lft forever
inet 192.168.150.111/24 brd 192.168.150.255 scope global secondary enp0s3
valid_lft forever preferred_lft forever
inet 192.168.150.112/24 brd 192.168.150.255 scope global secondary enp0s3
valid_lft forever preferred_lft forever
inet 192.168.150.113/24 scope global secondary enp0s3
valid_lft forever preferred_lft forever
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# ping 192.168.150.113
PING 192.168.150.113 (192.168.150.113) 56(84) bytes of data.
64 bytes from 192.168.150.113: icmp_seq=1 ttl=64 time=0.098 ms
64 bytes from 192.168.150.113: icmp_seq=2 ttl=64 time=0.255 ms
......
/etc/sysconfig/network-scripts/ifcfg-eth0 配置文件里并没有192.168.150.113，所以重启后该IP不会保留。
在线删除IP：
[root@centos7 ~]# ip addr del 192.168.150.113/24 dev enp0s3
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# nmcli -t -f IP4.ADDRESS dev show enp0s3
IP4.ADDRESS[1]:ip = 192.168.150.110/24, gw = 192.168.150.254
IP4.ADDRESS[2]:ip = 192.168.150.111/24, gw = 192.168.150.254
IP4.ADDRESS[3]:ip = 192.168.150.112/24, gw = 192.168.150.254
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# ip addr show enp0s3 scope global
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 08:00:27:15:35:d2 brd ff:ff:ff:ff:ff:ff
inet 192.168.150.110/24 brd 192.168.150.255 scope global enp0s3
valid_lft forever preferred_lft forever
inet 192.168.150.111/24 brd 192.168.150.255 scope global secondary enp0s3
valid_lft forever preferred_lft forever
inet 192.168.150.112/24 brd 192.168.150.255 scope global secondary enp0s3
valid_lft forever preferred_lft forever
四、使用子连接配置文件 ifcfg-*:n
子连接配置文件是 Centos6 常用的方法，即：如果当前网卡配置文件为 ifcfg-eth0，则子连接配置文件可以为 ifcfg-eth0:1，并且文件中需要写明 DEVICE=eth0:1 ， IPADDR=<新IP地址> 。
我们试试在Centos7 中是否也支持。理论上应该是不支持的，因为在Centos7的网络连接配置文件（即 ifcfg-*）中，DEVICE关键字已经具有了新的定义，即我们上篇说的“设备”。参考前面几页。
首先注释掉ifcfg-eth0中的其他地址，复制 ifcfg-eth0 为 ifcfg-eth0:1，编辑ifcfg-eth0:1， DEVICE 设为eth0:1 ，IP设为 192.168.150.119 ，然后 nmcli con reload ， nmcli dev con enp0s3
复制代码
[root@centos7 ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0
TYPE=Ethernet
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=no
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_PEERDNS=yes
IPV6_PEERROUTES=yes
IPV6_FAILURE_FATAL=no
NAME=eth0
UUID=295e1841-0ff3-4db9-8800-4e25fc2944da
ONBOOT=yes
IPADDR0=192.168.150.110
PREFIX0=24
GATEWAY0=192.168.150.254
DNS1=192.168.150.254
HWADDR=08:00:27:15:35:D2
#IPADDR1=192.168.150.111
#PREFIX1=24
#IPADDR2=192.168.150.112
#PREFIX2=24
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0:1
TYPE=Ethernet
BOOTPROTO=none
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=no
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_PEERDNS=yes
IPV6_PEERROUTES=yes
IPV6_FAILURE_FATAL=no
NAME=eth0:1
DEVICE=eth0:1
UUID=295e1841-0ff3-4db9-8800-4e25fc2944da
ONBOOT=yes
IPADDR0=192.168.150.119
PREFIX0=24
GATEWAY0=192.168.150.254
DNS1=192.168.150.254
HWADDR=08:00:27:15:35:D2
[root@centos7 ~]#
[root@centos7 ~]# nmcli con reload
[root@centos7 ~]# nmcli dev connect enp0s3
[root@centos7 ~]#
[root@centos7 ~]# nmcli -t -f IP4.ADDRESS dev show enp0s3
IP4.ADDRESS[1]:ip = 192.168.150.110/24, gw = 192.168.150.254
[root@centos7 ~]#
[root@centos7 ~]#
[root@centos7 ~]# ip addr show enp0s3 scope global
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 08:00:27:15:35:d2 brd ff:ff:ff:ff:ff:ff
inet 192.168.150.110/24 brd 192.168.150.255 scope global eth0:1
valid_lft forever preferred_lft forever
[root@centos7 ~]#
可以看到ifcfg-eth0:1里的新IP确实没有生效。
五、总结
•ip addr show 中显示的IP才是有效的。
•ip addr add 能在线添加IP，立即生效，但重启即丢。
•ip addr del 能在线删除IP，立即生效，但重启即丢。
•子连接(ifcfg-*:n)已经无效了。
•nmtui和编辑ifcfg-eth0 文件效果基本相同，��不能立即生效，必须 load 连接再重新connect网络设备，即：
nmcli con load /etc/sysconfig/network-scripts/ifcfg-eth0 或 nmcli reload
nmcli dev connect enp0s3