在使用linux的过程中如果安装了多台虚拟机，并且每台虚拟机都是由上一台虚拟机克隆出来的我们可能会出现联网连不上的问题，在linux的控制台输出ifconfg会出现以下信息：
[root@tiny ~]$ ifconfig
eth2 Link encap:Ethernet HWaddr 00:0C:29:FE:F8:14
inet6 addr: fe80::20c:29ff:fefe:f814/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:68 errors:0 dropped:0 overruns:0 frame:0
TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:7385 (7.2 KiB) TX bytes:2310 (2.2 KiB)
Interrupt:19 Base address:0x2024
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:8 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:480 (480.0 b) TX bytes:480 (480.0 b)
会报 UP BROADCAST RUNNING MULTICAST错误。这是因为mac地址设置的问题，在这里提供一个解决办法：
1. 切换至root用户
由于相关文件只能由root进行修改，因此我们先应该转换为root用户启动
[admin@tiny ~]$ su root
2.查看当前MAC地址相关信息
[root@tiny rules.d]# cat /etc/udev/rules.d/70-persistent-net.rules
# This file was automatically generated by the /lib/udev/write_net_rules
# program, run by the persistent-net-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single
# line, and change only the value of the NAME= key.
# PCI device 0x1022:0x2000 (pcnet32)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0c:29:49:e9:9d", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"
# PCI device 0x1022:0x2000 (vmxnet)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0c:29:13:e9:e2", ATTR{type}=="1", KERNEL=="eth*", NAME="eth1"
# PCI device 0x1022:0x2000 (vmxnet)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0c:29:fe:f8:14", ATTR{type}=="1", KERNEL=="eth*", NAME="eth2"
我们可以看到其中包含三块网卡信息分别是eth0,eth1,eth2，而我们使用eth2所以我们需要删除掉其他两块网卡信息。
[root@tiny rules.d]# vi /etc/udev/rules.d/70-persistent-net.rules
[root@tiny rules.d]# cat /etc/udev/rules.d/70-persistent-net.rules
# This file was automatically generated by the /lib/udev/write_net_rules
# program, run by the persistent-net-generator.rules rules file.
#
# You can modify it, as long as you keep each rule on a single
# line, and change only the value of the NAME= key.
# PCI device 0x1022:0x2000 (vmxnet)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:0c:29:fe:f8:14", ATTR{type}=="1", KERNEL=="eth*", NAME="eth2"
我们只留下eth2的网卡信息，我们记录下eth2的mac地址：00:0c:29:fe:f8:14。
4. 修改ifcfg-eth2中的信息
在这里我发现了一件非常尴尬的事情，在/etc/sysconfig/network-scripts/文件夹下没有ifcfg-eth2
[root@tiny network-scripts]# ls /etc/sysconfig/network-scripts/
ifcfg-eth0~ ifdown-ippp ifdown-tunnel ifup-isdn ifup-tunnel
ifcfg-eth1 ifdown-ipv6 ifup ifup-plip ifup-wireless
ifcfg-eth1~ ifdown-isdn ifup-aliases ifup-plusb init.ipv6-global
ifcfg-lo ifdown-post ifup-bnep ifup-post net.hotplug
ifdown ifdown-ppp ifup-eth ifup-ppp network-functions
ifdown-bnep ifdown-routes ifup-ippp ifup-routes network-functions-ipv6
ifdown-eth ifdown-sit ifup-ipv6 ifup-sit
但是，我们可以拷贝一个
[root@tiny network-scripts]# mv /etc/sysconfig/network-scripts/ifcfg-eth1 /etc/sysconfig/network-scripts/ifcfg-eth2
然后我们打开ifcfg-eth2
[root@tiny network-scripts]# cat /etc/sysconfig/network-scripts/ifcfg-eth2
DEVICE=eth1
TYPE=Ethernet
UUID=eeb8ed32-3b4d-45c4-b2fe-9c7b5fe4e2ac
ONBOOT=yes
NM_CONTROLLED=yes
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth1"
HWADDR=00:0C:29:49:E9:9D
LAST_CONNECT=1488606798
BOOTPROTO=static
IPADDR=192.168.132.114
NETMASK=255.255.255.0
GATEWAY=192.168.132.1
DNS1=210.31.249.20
mac地址和在70-persistent-net.rules中的mac并不一样，我们将70-persistent-net.rules中的mac地址复制过来，并且将DEVICE和NAME也做相应的修改
[root@tiny network-scripts]# vi /etc/sysconfig/network-scripts/ifcfg-eth2
[root@tiny network-scripts]# cat /etc/sysconfig/network-scripts/ifcfg-eth2
DEVICE=eth2
TYPE=Ethernet
UUID=eeb8ed32-3b4d-45c4-b2fe-9c7b5fe4e2ac
ONBOOT=yes
NM_CONTROLLED=yes
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth2"
HWADDR=00:0c:29:fe:f8:14
LAST_CONNECT=1488606798
BOOTPROTO=static
IPADDR=192.168.132.115
NETMASK=255.255.255.0
GATEWAY=192.168.132.1
DNS1=210.31.249.20
5. 重启服务，并测试
重启network，查看网卡信息，并测试联网情况 。执行下面的命令：
[root@tiny network-scripts]# service network restart
正在关闭接口 eth2： 设备状态：3 (断开连接)
[确定]
关闭环回接口： [确定]
弹出环回接口： [确定]
弹出界面 eth2： 活跃连接状态：激活的
活跃连接路径：/org/freedesktop/NetworkManager/ActiveConnection/23
[确定]
[root@tiny network-scripts]# ifconfig
eth2 Link encap:Ethernet HWaddr 00:0C:29:FE:F8:14
inet addr:192.168.132.115 Bcast:192.168.132.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fefe:f814/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1595 errors:0 dropped:0 overruns:0 frame:0
TX packets:117 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:159465 (155.7 KiB) TX bytes:33595 (32.8 KiB)
Interrupt:19 Base address:0x2024
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:8 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:480 (480.0 b) TX bytes:480 (480.0 b)
[root@tiny network-scripts]# ping 119.75.217.109
PING 119.75.217.109 (119.75.217.109) 56(84) bytes of data.
64 bytes from 119.75.217.109: icmp_seq=1 ttl=64 time=0.611 ms
64 bytes from 119.75.217.109: icmp_seq=2 ttl=64 time=0.261 ms
^C
--- 119.75.217.109 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1424ms
rtt min/avg/max/mdev = 0.261/0.436/0.611/0.175 ms
修改成功