KVM 宿主机上创建桥接网络
宿主机上执行#virsh iface-bridge etho br0
只能执行一次
创建名为bridge的网桥设备，并将现有网络设备接口附加到新网桥。新桥默认立即启动，
在启用STP且延迟为0的情况下；这些设置可以通过--no STP、--no start和延迟的整数秒数进行更改。所有IP地址
接口配置将移至新的桥接设备
iface-bridge interface bridge [--no-stp] [delay] [--no-start]
Create a bridge device named bridge, and attach the existing network device interface to the new bridge. The new bridge defaults to starting immediately,
with STP enabled and a delay of 0; these settings can be altered with --no-stp, --no-start, and an integer number of seconds for delay. All IP address
configuration of interface will be moved to the new bridge device.
See also iface-unbridge for undoing this operation.
~~ 有的可能会遇到报错如下：失败并且 终端断开连接，不要慌有解决办法
[root@localhost centos6.9-4]# virsh iface-bridge ens33 br0使用附加设备 br0 生成桥接 ens33 失败
Socket error Event: 32 Error: 10053.
Connection closing...Socket close.
Connection closed by foreign host.~~
解决办法
登上宿主机打开终端执行重启网络服务命令
皆可解决
CentOS7#systemctl restart network
CentOS8 #nmcli connection reload ens160
#nmcli connention up ens160
执行后Xshell重新连接 ，可以连上检查网络已有桥接网络 br0
[root@localhost ~]# grep -i "." /etc/sysconfig/network-scripts/ifcfg-
/etc/sysconfig/network-scripts/ifcfg-br0:DEVICE="br0"
/etc/sysconfig/network-scripts/ifcfg-br0:ONBOOT="yes"
/etc/sysconfig/network-scripts/ifcfg-br0:TYPE="Bridge"
/etc/sysconfig/network-scripts/ifcfg-br0:BOOTPROTO="none"
/etc/sysconfig/network-scripts/ifcfg-br0:IPADDR="10.1.3.2"
/etc/sysconfig/network-scripts/ifcfg-br0:NETMASK="255.255.255.0"
/etc/sysconfig/network-scripts/ifcfg-br0:GATEWAY="10.1.3.254"
/etc/sysconfig/network-scripts/ifcfg-br0:IPV6INIT="yes"
/etc/sysconfig/network-scripts/ifcfg-br0:IPV6_AUTOCONF="yes"
/etc/sysconfig/network-scripts/ifcfg-br0:DHCPV6C="no"
/etc/sysconfig/network-scripts/ifcfg-br0:STP="on"
/etc/sysconfig/network-scripts/ifcfg-br0:DELAY="0"
/etc/sysconfig/network-scripts/ifcfg-ens33:DEVICE="ens33"
/etc/sysconfig/network-scripts/ifcfg-ens33:ONBOOT="yes"
/etc/sysconfig/network-scripts/ifcfg-ens33:BRIDGE="br0"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:TYPE="Ethernet"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:PROXY_METHOD="none"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:BROWSER_ONLY="no"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:BOOTPROTO="none"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:DEFROUTE="yes"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:IPV4_FAILURE_FATAL="yes"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:IPV6INIT="yes"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:IPV6_AUTOCONF="yes"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:IPV6_DEFROUTE="yes"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:IPV6_FAILURE_FATAL="no"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:IPV6_ADDR_GEN_MODE="stable-privacy"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:NAME="ens33"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:UUID="68f524ae-37f5-4924-8c2b-c1f9042b13d9"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:DEVICE="ens33"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:ONBOOT="yes"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:IPADDR="10.1.3.2"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:PREFIX="24"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:GATEWAY="10.1.3.254"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:DNS1="8.8.8.8"
/etc/sysconfig/network-scripts/ifcfg-ens33.bak:IPV6_PRIVACY="no"
/etc/sysconfig/network-scripts/ifcfg-lo:DEVICE=lo
/etc/sysconfig/network-scripts/ifcfg-lo:IPADDR=127.0.0.1
/etc/sysconfig/network-scripts/ifcfg-lo:NETMASK=255.0.0.0
/etc/sysconfig/network-scripts/ifcfg-lo:NETWORK=127.0.0.0
/etc/sysconfig/network-scripts/ifcfg-lo:# If you're having problems with gated making 127.0.0.0/8 a martian,
/etc/sysconfig/network-scripts/ifcfg-lo:# you can change this to something else (255.255.255.255, for example)
/etc/sysconfig/network-scripts/ifcfg-lo:BROADCAST=127.255.255.255
/etc/sysconfig/network-scripts/ifcfg-lo:ONBOOT=yes
/etc/sysconfig/network-scripts/ifcfg-lo:NAME=loopback
**[root@localhost ~]# ll /etc/sysconfig/network-scripts/ifcfg-***
-rw-r--r--. 1 root root 187 12月 31 15:55 /etc/sysconfig/network-scripts/ifcfg-br0
-rw-------. 1 root root 41 12月 31 15:55 /etc/sysconfig/network-scripts/ifcfg-ens33
-rw-r--r--. 1 root root 395 7月 8 06:58 /etc/sysconfig/network-scripts/ifcfg-ens33.bak
-rw-r--r--. 1 root root 254 8月 24 2018 /etc/sysconfig/network-scripts/ifcfg-lo
通过man iface-bridge 查看命令用法
虚机网络设置
#virsh destroy vm1
#virsh edit vm1
编辑文件两处如下截图
#virsh start vm1 启动虚机
为虚机设置IP编辑网络配置文件或者配置DHCP自动获取（上层网络编辑器是否开启DHCP）
查看虚机内部网络信息
#virsh
[root@localhost ~]# virsh
欢迎使用 virsh，虚拟化的交互式终端。
输入：'help' 来获得命令的帮助信息
'quit' 退出
virsh # iface-
iface-begin iface-commit iface-destroy iface-edit iface-mac iface-rollback iface-unbridge
iface-bridge iface-define iface-dumpxml iface-list iface-name iface-start iface-undefine
virsh # net-list
名称 状态 自动开始 持久
default 活动 是 是
virsh # net-edit default
未更改网络 default XML 配置
virsh #