一、 问题现象
某客户有一台安装RHEL6.5系统的服务器，该服务器需要配置内网和外网两个IP地址，系统配置好IP地址重启网卡服务后，通过内、外网IP地址都能正常连接。过一会儿后就连接不正常了，
该服务器无法通过外网IP地址远程连接，而通过内网IP地址却能远程，后来远程ifconfig查看网卡配置，发现外网IP丢失，两块网卡全变成了内网IP(如下图所示)
二、问题原因
该系统在安装的时候是安装了图形化界面服务，默认会安装 NetworkManager 管理服务，NetworkManager服务启动以后导致系统内部的网络配置出现紊乱。
三、解决方案
1、执行chkconfig --list命令查看NetworkManager服务是否开机启动：
2、如果该服务为启动状态，执行service NetworkManager stop或者/etc/init.d/NetworkManager stop 停止 NetworkManager 服务。
3、执行chkconfig NetworkManager off命令禁止NetworkManager 开机启动。
4、执行 /etc/init.d/network restart 重启服务器的网络检查，之后就恢复正常。
5.所以配置IP别名的时候，需要先关闭NetworkManager 服务。
6 IP别名（一个物理网卡添加多个IP地址）
[root@192 ~]# ifconfig
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.132.188 netmask 255.255.255.0 broadcast 192.168.132.255
inet6 fe80::f3cb:e9b0:cc85:56ab prefixlen 64 scopeid 0x20<link>
ether 00:0c:29:25:af:d7 txqueuelen 1000 (Ethernet)
RX packets 3445892 bytes 4840270149 (4.5 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 256138 bytes 31798039 (30.3 MiB)
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 1 (Local Loopback)
RX packets 33 bytes 2920 (2.8 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 33 bytes 2920 (2.8 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
virbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.122.1 netmask 255.255.255.0 broadcast 192.168.122.255
ether 52:54:00:dc:f6:77 txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
vnet0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet6 fe80::fc54:ff:fe2e:519c prefixlen 64 scopeid 0x20<link>
ether fe:54:00:2e:51:9c txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 23037 bytes 1198156 (1.1 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
[root@192 ~]#
为ens33 网卡添加一个别名
[root@192 ~]# ip addr add 192.168.1.200/24 dev ens33 label ens33:0
[root@192 ~]# ifconfig
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.132.188 netmask 255.255.255.0 broadcast 192.168.132.255
inet6 fe80::f3cb:e9b0:cc85:56ab prefixlen 64 scopeid 0x20<link>
ether 00:0c:29:25:af:d7 txqueuelen 1000 (Ethernet)
RX packets 3446156 bytes 4840293287 (4.5 GiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 256290 bytes 31817767 (30.3 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
ens33:0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.1.200 netmask 255.255.255.0 broadcast 0.0.0.0
ether 00:0c:29:25:af:d7 txqueuelen 1000 (Ethernet)
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 1 (Local Loopback)
RX packets 33 bytes 2920 (2.8 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 33 bytes 2920 (2.8 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
virbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.122.1 netmask 255.255.255.0 broadcast 192.168.122.255
ether 52:54:00:dc:f6:77 txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 0 bytes 0 (0.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
vnet0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet6 fe80::fc54:ff:fe2e:519c prefixlen 64 scopeid 0x20<link>
ether fe:54:00:2e:51:9c txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 23126 bytes 1202784 (1.1 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
[root@192 ~]#