1）现象说明
公司IDC机房里的一台线上服务器硬件报警，最后排查发现服务器主板坏了，随即联系厂商进行更换主板，最后更换后，登录服务器，发现网卡绑定及ip信息都在，但是ip却ping不通了，进一步排查，重启网卡，提示之前的eth0和eth1网卡设备发现不了了，也就是说服务器主板更换后，之前的网卡设备都识别不了了！
主板更换后，重启并登陆服务器，发现之前的网卡设备（eth0、eth1、eth2、eth3）都没有了！
[root@kevin01 ~]# ifconfig -a
bond0 Link encap:Ethernet HWaddr 08:94:EF:5E:AE:72
inet addr:192.168.10.20 Bcast:192.168.10.255 Mask:255.255.255.0
inet6 addr: fe80::a94:efff:fe5e:ae72/64 Scope:Link
UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1
RX packets:75582 errors:0 dropped:0 overruns:0 frame:0
TX packets:58537 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:5890233 (5.6 MiB) TX bytes:4390537 (4.1 MiB) 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:65536 Metric:1
RX packets:26 errors:0 dropped:0 overruns:0 frame:0
TX packets:26 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1983 (1.9 KiB) TX bytes:1983 (1.9 KiB) usb0 Link encap:Ethernet HWaddr 0A:94:EF:5E:AE:79
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) 之前的网卡设备和bond绑定的配置信息都还在（bond绑定网卡操作：http://www.cnblogs.com/kevingrace/p/7966511.html）
[root@kevin ~]# cd /etc/sysconfig/network-scripts/
[root@kevin network-scripts]# ls
ifcfg-bond0 ifcfg-lo ifdown-ib ifdown-ppp ifup-aliases ifup-ipv6 ifup-ppp init.ipv6-global
ifcfg-eth0 ifcfg-usb0 ifdown-ippp ifdown-routes ifup-bnep ifup-isdn ifup-routes net.hotplug
ifcfg-eth1 ifdown ifdown-ipv6 ifdown-sit ifup-eth ifup-plip ifup-sit network-functions
ifcfg-eth2 ifdown-bnep ifdown-isdn ifdown-tunnel ifup-ib ifup-plusb ifup-tunnel network-functions-ipv6
ifcfg-eth3 ifdown-eth ifdown-post ifup ifup-ippp ifup-post ifup-wireless [root@kevin ~]# /etc/init.d/network restart
......
报错说没有发现eth0和eth1网卡 [root@kevin ~]# ipdown eth0
报错提示说没有发现eth0网卡
2）产生原因
这是因为服务器更换了主板或网卡，mac地址改变所导致的。系统加载网卡驱动后会去读一个文件（即/etc/udev/rules.d/70-persistent-net.rules），这个文件是一个缓冲文件，包含了网卡的mac地址，因为更换了主板，网卡的mac地址也变了，但是这个文件的mac地址还没变，还是之前坏了的主板的上面的网卡的MAC地址，这样系统在加载网卡，读取这个文件的时候读取的是之前网卡的mac地址，和现在更换后主板后的网卡mac地址不一致导致混乱，所以就识别不了当前网卡；
3）解决办法
一般来说，删除/etc/udev/rules.d/70-persistent-net.rules文件（或者把这个文件重新命名 或者 清空该文件内容），重启服务器就可以解决了，重启后会重新生成这个文件，
这样就顺利解决这个问题了！这里注意下，由于我的这台服务器绑定了网卡，所以重启网卡后，还需要进行modprobe命令使得网卡绑定生效，大致步骤如下：
# mv /etc/udev/rules.d/70-persistent-net.rules /etc/udev/rules.d/70-persistent-net.rules.bak20180307
# init 6 重启服务器后，查看/etc/udev/rules.d/70-persistent-net.rules文件，发现没有eth0、eth1、eth3、eth4的网卡信息（mac和设备名称）
[root@kevin network-scripts]# 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 0x14e4:0x1657 (tg3)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="****", ATTR{type}=="1", KERNEL=="eth*" # PCI device 0x14e4:0x1657 (tg3)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="****", ATTR{type}=="1", KERNEL=="eth*" # PCI device 0x14e4:0x1657 (tg3)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="****", ATTR{type}=="1", KERNEL=="eth*" # PCI device 0x14e4:0x1657 (tg3)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="****", ATTR{type}=="1", KERNEL=="eth*" 然后重启网卡等操作
[root@kevin ~]# modprobe bonding
[root@kevin ~]# /etc/init.d/network restart
[root@kevin ~]# modprobe bonding 接着ifconfig查看，发现eth0、eth1、eth2、eth3网卡设备都能识别了
[root@kevin ~]# ifconfig -a
bond0 Link encap:Ethernet HWaddr 08:94:EF:5E:AE:72
inet addr:192.168.10.20 Bcast:192.168.10.255 Mask:255.255.255.0
inet6 addr: fe80::a94:efff:fe5e:ae72/64 Scope:Link
UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1
RX packets:108809 errors:0 dropped:0 overruns:0 frame:0
TX packets:84207 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:8471111 (8.0 MiB) TX bytes:6322341 (6.0 MiB) eth0 Link encap:Ethernet HWaddr 08:94:EF:5E:AE:72
UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
RX packets:38051 errors:0 dropped:0 overruns:0 frame:0
TX packets:14301 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2869726 (2.7 MiB) TX bytes:944276 (922.1 KiB)
Interrupt:16 eth1 Link encap:Ethernet HWaddr 08:94:EF:5E:AE:72
UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
RX packets:69158 errors:0 dropped:0 overruns:0 frame:0
TX packets:68615 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:5469647 (5.2 MiB) TX bytes:5279012 (5.0 MiB)
Interrupt:17 eth2 Link encap:Ethernet HWaddr 08:94:EF:5E:AE:74
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
Interrupt:16 eth3 Link encap:Ethernet HWaddr 08:94:EF:5E:AE:75
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
Interrupt:17 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:65536 Metric:1
RX packets:26 errors:0 dropped:0 overruns:0 frame:0
TX packets:26 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1983 (1.9 KiB) TX bytes:1983 (1.9 KiB) usb0 Link encap:Ethernet HWaddr 0A:94:EF:5E:AE:79
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) 在查看/etc/udev/rules.d/70-persistent-net.rules文件，发现eth0、eth1、eth2、eth3网卡及其mac地址信息都有了
[root@kevin ~]# 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 0x14e4:0x1657 (tg3)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="08:94:ef:5e:ae:75", ATTR{type}=="1", KERNEL=="eth*", NAME="eth3" # PCI device 0x14e4:0x1657 (tg3)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="08:94:ef:5e:ae:72", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0" # PCI device 0x14e4:0x1657 (tg3)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="08:94:ef:5e:ae:73", ATTR{type}=="1", KERNEL=="eth*", NAME="eth1" # PCI device 0x14e4:0x1657 (tg3)
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="08:94:ef:5e:ae:74", ATTR{type}=="1", KERNEL=="eth*", NAME="eth2" 接着尝试ping其他机器
[root@kevin ~]# ping 192.168.10.23
PING 192.168.10.23 (192.168.10.23) 56(84) bytes of data.
64 bytes from 192.168.10.23: icmp_seq=1 ttl=64 time=0.030 ms
64 bytes from 192.168.10.23: icmp_seq=2 ttl=64 time=0.016 ms
64 bytes from 192.168.10.23: icmp_seq=3 ttl=64 time=0.016 ms 如果ping不通的话，多执行下面命令
[root@kevin ~]# modprobe bonding
温馨提示：有时候重启后还是出现以上情况，对比之前的/etc/udev/rules.d/70-persistent-net.rules文件，新的文件mac地址和name已经改变，name=eth0,和之前name=em1的名字不同；
