因项目需测试，虚拟机上用centos7和centos6搭建了四五台数据库，准备做多实例主备测试，其中一台的LINUX每次需要重启一次网络服务才能连接，后来，网络服务启动正常后，干脆就是自动关闭了，报错如下：

－－－网络异常现象 

root@ora112 network-scripts]# systemctl status network.service ● network.service - LSB: Bring up/down networking    Loaded: loaded (/etc/rc.d/init.d/network; bad; vendor preset: disabled)    Active: active (exited) since Sun 2019-12-22 13:07:02 CST; 18s ago      Docs: man:systemd-sysv-generator(8)   Process: 22579 ExecStop=/etc/rc.d/init.d/network stop (code=exited, status=0/SUCCESS)   Process: 22761 ExecStart=/etc/rc.d/init.d/network start (code=exited, status=0/SUCCESS)

Dec 22 13:06:57 ora112.oracle.com systemd[1]: Starting LSB: Bring up/down networking... Dec 22 13:06:57 ora112.oracle.com network[22761]: Bringing up loopback interface:  [  OK  ] Dec 22 13:07:02 ora112.oracle.com NET[22996]: /etc/sysconfig/network-scripts/ifup-post : updated /etc/resolv.conf Dec 22 13:07:02 ora112.oracle.com network[22761]: Bringing up interface ens33:  [  OK  ] Dec 22 13:07:02 ora112.oracle.com systemd[1]: Started LSB: Bring up/down networking.

[root@ora112 network-scripts]# ip add 1: lo: 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: ens33: mtu 1500 qdisc pfifo_fast state UP group default qlen 1000     link/ether 00:0c:29:f5:96:35 brd ff:ff:ff:ff:ff:ff     inet6 fe80::bfa0:8a12:c3e9:c6f5/64 scope link noprefixroute 

处理过程：       使用命令journalctl -xe 进行日志查询。（journalctl 用来查询 systemd-journald 服务收集到的日志）报错：  [1576991788.0680] device (ens33): Activation: failed for connection 'Wired c

查看网络连接情况

[root@ora112 network-scripts]# nmcli connection show NAME                UUID                                  TYPE      DEVICE  Wired connection 1  dbd4fd1e-e42f-3567-82fb-06cdca822187  ethernet  --     

--rm删除掉配置文件，使用nmtui工具，重新生成配置文件  [root@ora112 network-scripts]#rm -f ifcfg-ens33  [root@ora112 network-scripts]#vi ifcfg-ens33 [root@ora112 network-scripts]#nmtui EDIT "wired connection1" --->profile name:ens33

－－启动后仍报错 [root@ora112 network-scripts]# service network start Starting network (via systemctl):  Job for network.service failed because the control process exited with error code. See "systemctl status network.service" and "journalctl -xe" for details.                                                            [FAILED]－－检查是因使用了DHCP服务，获取失败，更改配置文件指定静态IP [root@ora112 network-scripts]# vi ifcfg-ens33  HWADDR=00:0C:29:F5:96:35 TYPE=Ethernet NAME=ens33 UUID=dbd4fd1e-e42f-3567-82fb-06cdca822187 BOOTPROTO=on ONBOOT=on IPADDR=192.168.23.21 GATEWAY=192.168.23.2 －－再次启动并测试，恢复正常   [root@ora112 network-scripts]# service network start Starting network (via systemctl):                          [  OK  ]

[root@ora112 network-scripts]# !ping ping 192.168.23.20 PING 192.168.23.20 (192.168.23.20) 56(84) bytes of data. 64 bytes from 192.168.23.20: icmp_seq=1 ttl=64 time=0.104 ms 64 bytes from 192.168.23.20: icmp_seq=2 ttl=64 time=0.094 ms 64 bytes from 192.168.23.20: icmp_seq=3 ttl=64 time=0.066 ms

然后，重启后发现，网络又断开，关闭NetworkManager.service服务，并从启动列表移除。再次重启，恢复正常 [root@ora112 network-scripts]# /bin/systemctl stop NetworkManager.service [root@ora112 network-scripts]# chkconfig NetworkManager off

根据以往实验，总结网络异常和解决方式如下：

（1，与NetworkManager 服务有冲突，连接关闭 NetworkManger 服务  service NetworkManager stop chkconfig NetworkManager off 

（2,和配置文件的MAC地址不匹配，使用ip addr（或ifconfig）查看mac地址，更改IPADD即可 （3，/etc/sysconfig/network-scripts网卡配置文件格式有误，删掉空格或乱码 （4，网络模块加载失败，重新加载网络模块

（5，CP虚机后，MAC或网上uuid冲突。删除UDEV下的配置，重启