默认路径为：
/etc/sysconfig/network-scripts/ifcfg-enp0s3
之前安装的时候，设置是好的，不知为何过了一段时间就无效果了。
在centos7下 获得mac的值。
在CentOS7下获取Mac地址的值
[root@localhost shell]# ifconfig eth0
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.2.10 netmask 255.255.255.0 broadcast 192.168.2.255
inet6 fe80::20c:29ff:fed7:8537 prefixlen 64 scopeid 0x20<link>
ether 00:0c:29:d7:85:37 txqueuelen 1000 (Ethernet)
RX packets 137188 bytes 184028883 (175.5 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 42678 bytes 3437016 (3.2 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
[root@localhost shell]# ifconfig eth0 |egrep "ether"
ether 00:0c:29:d7:85:37 txqueuelen 1000 (Ethernet)
[root@localhost shell]# ifconfig eth0 |egrep "ether" |awk '{print $2}'
00:0c:29:d7:85:37
[root@localhost shell]#
尝试方式2:
[root@CentOS7x64 ~]# getenforce
setenforce 0
虚拟机器中，配置了静态ip 但是 允许1分钟后就自动消失了，
采用ipconfig 查看，发现ip丢失了。
又重启了 service network restart后就又有了ip。但是，过不了多久，继续丢失这类现象。
--解决方案：将设置成了HOst-only 模式。
缺点：无法上网。
采用方式，重新安装一个新的续集，看是否可以通过“网络桥接‘进行上网。
---
vi /etc/sysconfig/network-scripts/ifcfg-eno16777736里面的name和device，并把配置文件名改为ifcfg-eth0。重启网络：systemctl restart network.service。后来因重启失败还原为原来的信息，以为会正常，但仍没有解决。
# systemctl restart network.service
Job for network.service failed because the control process exited with error code. See "systemctl status network.service" and "journalctl -xe" for details.
根据提示查看网卡信息
# systemctl status network.service
查看日志
# cat /var/log/messages |grep network
Jul 4 10:05:10 dg-p systemd: Starting LSB: Bring up/down networking...
Jul 4 10:05:10 dg-p network: Bringing up loopback interface: Could not load file '/etc/sysconfig/network-scripts/ifcfg-lo'
Jul 4 10:05:10 dg-p network: Could not load file '/etc/sysconfig/network-scripts/ifcfg-lo'
Jul 4 10:05:10 dg-p network: Could not load file '/etc/sysconfig/network-scripts/ifcfg-lo'
Jul 4 10:05:10 dg-p network: Could not load file '/etc/sysconfig/network-scripts/ifcfg-lo'
Jul 4 10:05:10 dg-p network: [ OK ]
Jul 4 10:05:11 dg-p network: Bringing up interface eno16777736: Error: Connection activation failed: No suitable device found for this connection.
Jul 4 10:05:11 dg-p network: [FAILED]
Jul 4 10:05:11 dg-p network: RTNETLINK answers: File exists
Jul 4 10:05:11 dg-p network: RTNETLINK answers: File exists
Jul 4 10:05:11 dg-p network: RTNETLINK answers: File exists
Jul 4 10:05:11 dg-p network: RTNETLINK answers: File exists
Jul 4 10:05:11 dg-p network: RTNETLINK answers: File exists
Jul 4 10:05:11 dg-p network: RTNETLINK answers: File exists
Jul 4 10:05:11 dg-p network: RTNETLINK answers: File exists
Jul 4 10:05:11 dg-p network: RTNETLINK answers: File exists
Jul 4 10:05:11 dg-p network: RTNETLINK answers: File exists
Jul 4 10:05:11 dg-p systemd: network.service: control process exited, code=exited status=1
Jul 4 10:05:11 dg-p systemd: Failed to start LSB: Bring up/down networking.
Jul 4 10:05:11 dg-p systemd: Unit network.service entered failed state.
Jul 4 10:05:11 dg-p systemd: network.service failed.
解决：
百度后很多说是MAC地址或者NetworkManager服务的问题，试过后仍未解决。解铃还须系铃人，试着修改网卡名---
（1）修改网卡名和配置文件
# mv /etc/sysconfig/network-scripts/ifcfg-eno16777736 /etc/sysconfig/network-scripts/ifcfg-eth0
修改配置文件里面name和device
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
TYPE=Ethernet
BOOTPROTO=static 实际我配置的是dch
DEFROUTE=yes
PEERDNS=yes
PEERROUTES=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_PEERDNS=yes
IPV6_PEERROUTES=yes
IPV6_FAILURE_FATAL=no
NAME=eth0
UUID=d890d6e6-01f6-4063-bf70-cd4e1787d0a8
HWADDR=00:50:56:8b:57:82 #这里原文件没有，手动添加上去
DEVICE=eth0
ONBOOT=yes
#IPADDR=192.168.70.42--我没有配置，自动获取的
#NETMASK=255.255.255.0
#GATEWAY=192.168.70.254
（2）修改/etc/sysconfig/grub，添加net.ifnames=0 biosdevname=0
# vi /etc/sysconfig/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="crashkernel=auto rd.lvm.lv=centos/root rd.lvm.lv=centos/swap net.ifnames=0 biosdevname=0rhgb quiet"
GRUB_DISABLE_RECOVERY="true"
（3）手动生成70-persistent-net.rules以及其他方法
查看接口的MAC地址
# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eno16777728: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP mode DEFAULT qlen 1000
link/ether 00:0c:29:28:ac:54 brd ff:ff:ff:ff:ff:ff
生成文件
# vi /etc/udev/rules.d/70-persistent-net.rules
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0c:29:28:ac:54", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"
或
#grub2-mkconfig -o /boot/grub2/grub.cfg #这个没有试过，有兴趣的可以自己试试
重启机器:
# reboot
---尝试效果：：：不行。失败了。
大招：
重启了我路由器，一切都可以了。
总共花费了2天时间。