KVM虚拟机与宿主机失联解决办法
部分集群的KVM集群在重启物理机后发现虚拟机网络故障，具体表现为ping不通网关和宿主机，也无法连接外网
首先分别检查宿主机和虚拟机网卡配置文件和路由是否正确
然后使用bcrtl检查宿主机网络桥接状态：
[root@node084 ~]# brctl show
bridge name bridge id STP enabled interfaces
br-13e4c7e43788 8000.024222969321 no
br-b7a940d7d211 8000.0242ac89ed2a no
br0 8000.ac1f6b1aca54 no eno1
docker0 8000.02421cc19f82 no vethe5249c6
virbr0 8000.5254004f8ee0 yes virbr0-nic可以看到br0虚拟网口只绑定了一个eno1的物理网口，除此之外没有任何虚拟网口。问题定位到了，下一步获取宿主机下所有虚拟网卡：
[root@node084 ~]# ip a |grep -i vnet*
40: vnet3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000
42: vnet0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000
44: vnet4: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000
48: vnet1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN group default qlen 1000使用brctl依次绑定虚拟网卡到br0网桥
[root@node084 ~]# brctl addif br0 vnet3
[root@node084 ~]# brctl addif br0 vnet0
[root@node084 ~]# brctl addif br0 vnet4
[root@node084 ~]# brctl addif br0 vnet1
[root@node084 ~]# brctl show
bridge name bridge id STP enabled interfaces
br-13e4c7e43788 8000.024222969321 no
br-b7a940d7d211 8000.0242ac89ed2a no
br0 8000.ac1f6b1aca54 no eno1
vnet0
vnet1
vnet3
vnet4
docker0 8000.02421cc19f82 no vethe5249c6
virbr0 8000.5254004f8ee0 yes virbr0-nic虚拟机恢复正常
[root@node084 ~]# ping 172.26.5.32
PING 172.26.5.32 (172.26.5.32) 56(84) bytes of data.
64 bytes from 172.26.5.32: icmp_seq=1 ttl=63 time=0.151 ms
64 bytes from 172.26.5.32: icmp_seq=2 ttl=63 time=0.117 ms
64 bytes from 172.26.5.32: icmp_seq=3 ttl=63 time=0.135 ms
64 bytes from 172.26.5.32: icmp_seq=4 ttl=63 time=0.143 ms
64 bytes from 172.26.5.32: icmp_seq=5 ttl=63 time=0.140 ms
^C
--- 172.26.5.32 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 3999ms
rtt min/avg/max/mdev = 0.117/0.137/0.151/0.013 ms
PS.
NetworkManager服务也会影响网桥的端口绑定，若开启NetworkManager服务可能会导致虚拟机无法访问外网!