宿主机配置，尤其注意将br0配置到stp协议里去，改完重启宿主机
root@xiangxin-B250M-D2V:/home/xiangxin# vi /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
#auto enp3s0
#iface enp3s0 inet static
#pre-up ifconfig enp3s0 hw ether e0:d5:5e:7f:31:97
#address 192.168.0.131
#netmask 255.255.255.0
#gateway 192.168.0.1
#dns-nameserver 114.114.114.114
#原网卡名为enp3s0，
auto br0
iface br0 inet static
address 192.168.0.131
netmask 255.255.255.0
gateway 192.168.0.1
bridge_ports enp3s0
bridge_stp on
bridge_fd 9
bridge_hello 2
bridge_maxage 12
dns-nameservers 114.114.114.114
#auto enp3s0
#iface enp3s0 inet manual
#auto tap0
#iface tap0 inet manual
#pre-up tunctl -t tap0 -u root
#pre-up ifconfig tap0 0.0.0.0 promisc up
#post-up brctl addif br0 tap0
启动网桥接口
tunctl -t tap0
brctl addif br0 tap0
ifconfig tap0 0.0.0.0 promisc up
brctl showstp br0
虚拟机启动命令
#创建虚拟磁盘
qemu-img create -f qcow2 ubuntu.img 10G
#安装系统
qemu-system-x86-64 -enable-kvm \
-hda ubuntu.img \
-boot d \
-cdrom ./ubuntu-16.04.6-desktop-amd64.iso \
-m 2048
#启动虚拟机
qemu-system-x86-64 -enable-kvm \
-boot -c \
-drive file=/wj/Qemu/ubuntu.img,if=virtio \
-m 2048 \
-smp 2 \
-netdev tap,ifname=tap0,script=no,downscript=no,id=net0 \
#-netdev tap,script=/wj/Qemu/qemu-ifup,downscript=no,id=net0 \
-device virtio-net-pci,netdev=ne0,mac=00:11:22:33:44:AB
参数及可加参数说明：
-daemonize表示在后台运行
-m 2048分配的内存
qemu-ifup脚本，可选，若使用上述命令启动了tap0，则不需要使用
root@xiangxin-B250M-D2V:/wj/Qemu# cat qemu-ifup
#!/bin/bash
switch=br0
if [ -n "$1" ]; then
ip link set $1 up
sleep 1
brctl addif ${switch} $1
exit 0
else
echo "Error: no interface specified"
exit 1
fi
虚拟机配置，完了重启虚拟机
test@test-Standard-PC-i440FX-PIIX-1996:~$ vi /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
auto ens3
iface ens3 inet static
address 192.168.0.181
netmask 255.255.255.0
gateway 192.168.0.1
dns-nameservers 114.114.114.114
bridge_fd 9
bridge_hello 2
bridge_maxage 12
bridge_stp on
