CentOS6.3 KVM如何设置网卡为桥接模式
	的默认网络模式为NAT,就是说借助宿主机模式上网,现在我们想改成,这样外界就可以直接和宿主机里的虚拟机通讯了。 
	1,首先看一下默认的网络设置 
复制代码
代码如下:
	
	# cat /etc/libvirt/qemu/networks/default.xml 
	<network> 
	<name>default</name> 
	<uuid>1f118032-0345-4725-adcf-6b94f6aca19c</uuid> 
	<bridge name="virbr0" /> 
	<mac address='52:54:00:F1:6B:6E'/> 
	<forward/> 
	<ip address="192.168.122.1" netmask="255.255.255.0"> 
	<dhcp> 
	<range start="192.168.122.2" end="192.168.122.254" /> 
	</dhcp> 
	</ip> 
	</network> 
	
	2,再看一下虚拟机配置文件里面的网络设置 
	#cat /etc/libvirt/qemu/ubuntu10.04.xml 
	<!-- 
	WARNING: THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE 
	OVERWRITTEN AND LOST. Changes to this xml configuration should be made using: 
	virsh edit ubuntu10.04 
	or other application using the libvirt API. 
	--> 
	<domain type='kvm'> 
	<name>ubuntu10.04</name> 
	<uuid>2eeb1395-39a2-a169-4da3-f22b20a1d34f</uuid> 
	<memory unit='KiB'>1048576</memory> 
	<currentMemory unit='KiB'>1048576</currentMemory> 
	<vcpu placement='static'>1</vcpu> 
	<os> 
	<type arch='x86_64' machine='rhel6.3.0'>hvm</type> 
	<boot dev='hd'/> 
	</os> 
	<features> 
	<acpi/> 
	<apic/> 
	<pae/> 
	</features> 
	<clock offset='utc'/> 
	<on_poweroff>destroy</on_poweroff> 
	<on_reboot>restart</on_reboot> 
	<on_crash>restart</on_crash> 
	<devices> 
	<emulator>/usr/libexec/qemu-kvm</emulator> 
	<disk type='file' device='disk'> 
	<driver name='qemu' type='raw' cache='none'/> 
	<source file='/var/lib/libvirt/images/ubuntu10.04.img'/> 
	<target dev='vda' bus='virtio'/> 
	<address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/> 
	</disk> 
	<disk type='block' device='cdrom'> 
	<driver name='qemu' type='raw'/> 
	<target dev='hdc' bus='ide'/> 
	<readonly/> 
	<address type='drive' controller='0' bus='1' target='0' unit='0'/> 
	</disk> 
	<controller type='usb' index='0'> 
	<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/> 
	</controller> 
	<controller type='ide' index='0'> 
	<address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x1'/> 
	</controller> 
	<interface type='bridge'> 原来是interface type='default' 
	<mac address='52:54:00:50:58:7e'/> 
	<source bridge='br1'/> 原来是source network='default',这里的br1要根据你的物理下面有讲 
	<model type='virtio'/> 
	<address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/> 
	</interface> 
	<serial type='pty'> 
	<target port='0'/> 
	</serial> 
	<console type='pty'> 
	<target type='serial' port='0'/> 
	</console> 
	<input type='mouse' bus='ps2'/> 
	<graphics type='vnc' port='-1' autoport='yes'/> 
	<sound model='ich6'> 
	<address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/> 
	</sound> 
	<video> 
	<model type='cirrus' vram='9216' heads='1'/> 
	<address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/> 
	</video> 
	<memballoon model='virtio'> 
	<address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/> 
	</memballoon> 
	</devices> 
	</domain> 
	[/code] 
	3,改完之后要更新一下配置文件 
	# virsh define ubuntu10.04.xml 
	定义域 ubuntu10.04(从 ubuntu10.04.xml) 
	#然后就可以virsh start ubuntu10.04了,不过现在物理网卡这块还没有改好 
	4,物理网卡可以手动更改,不过现在有现成的工具包,可以用这个更改 
	#wget http://www.convirture.com/downloads/convirture-tools/2.0.1/convirture-tools-2.0.1.tar.gz 
	# tar zxvf convirture-tools-2.0.1.tar.gz 
	# /root/convirture-tools/install/managed_server/scripts/convirt-tool --bridge setup 
	我的这里出现了点小问题,发现网络没起来,所以不要远程来做这个操作,主要原因是里面的配置文件有点需要 
	小的更改,我的是UUID注释了。 
	# ls ifcfg-* 
	ifcfg-br1 ifcfg-br2 ifcfg-br3 ifcfg-br4 ifcfg-em1 ifcfg-em2 ifcfg-em3 ifcfg-em4 ifcfg-lo 
	我这里有四个物理网卡,所以生成了四个bridge,不过真实用的只有br1 
	这个工具好有一个好处就是保存了原配置文件,如果你不想用时还可以还原 
	# ls saved.ifcfg-em* 
	saved.ifcfg-em1.20121128.101114 saved.ifcfg-em3.20121128.101114 
	saved.ifcfg-em2.20121128.101114 saved.ifcfg-em4.20121128.101114 
	看下ifceg-em1 
	# cat ifcfg-em1 
	DEVICE="em1" 
	#BOOTPROTO=none 
	NM_CONTROLLED="yes" 
	ONBOOT=yes 
	TYPE="Ethernet" 
	#UUID="3bc7fdcc-42b1-4223-b202-e697305897c8" 
	#IPADDR172.16.10.81 
	PREFIX=24 
	GATEWAY=172.16.10.254 
	DNS1=172.16.10.5 
	DEFROUTE=yes 
	IPV4_FAILURE_FATAL=yes 
	IPV6INIT=no 
	NAME="System em1" 
	HWADDR=90:B1:1C:20:4D:A5 
	BRIDGE=br1 
	看下ifcfg-br1 
	# cat ifcfg-br1 
	DEVICE="br1" 
	BOOTPROTO=none 
	NM_CONTROLLED="yes" 
	ONBOOT=yes 
	#UUID="3bc7fdcc-42b1-4223-b202-e697305897c8" 
	IPADDR=172.16.10.81 
	PREFIX=24 
	GATEWAY=172.16.10.254 
	DNS1=172.16.10.5 
	DEFROUTE=yes 
	IPV4_FAILURE_FATAL=yes 
	IPV6INIT=no 
	NAME="System br1" 
	TYPE=Bridge 
	最后看下网卡 
	# ifconfig 
	br1 Link encap:Ethernet HWaddr 90:B1:1C:20:4D:A5 
	inet addr:172.16.10.81 Bcast:172.16.10.255 Mask:255.255.255.0 
	inet6 addr: fe80::92b1:1cff:fe20:4da5/64 Scope:Link 
	UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 
	RX packets:10219 errors:0 dropped:0 overruns:0 frame:0 
	TX packets:3776 errors:0 dropped:0 overruns:0 carrier:0 
	collisions:0 txqueuelen:0 
	RX bytes:576031 (562.5 KiB) TX bytes:15928008 (15.1 MiB) 
	em1 Link encap:Ethernet HWaddr 90:B1:1C:20:4D:A5 
	inet6 addr: fe80::92b1:1cff:fe20:4da5/64 Scope:Link 
	UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 
	RX packets:10362 errors:0 dropped:0 overruns:0 frame:0 
	TX packets:13131 errors:0 dropped:0 overruns:0 carrier:0 
	collisions:0 txqueuelen:1000 
	RX bytes:766684 (748.7 KiB) TX bytes:16489098 (15.7 MiB) 
	Interrupt:35 
	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:144411 errors:0 dropped:0 overruns:0 frame:0 
	TX packets:144411 errors:0 dropped:0 overruns:0 carrier:0 
	collisions:0 txqueuelen:0 
	RX bytes:147381248 (140.5 MiB) TX bytes:147381248 (140.5 MiB) 
	virbr0 Link encap:Ethernet HWaddr 52:54:00:F1:6B:6E 
	inet addr:192.168.122.1 Bcast:192.168.122.255 Mask:255.255.255.0 
	UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 
	RX packets:2028 errors:0 dropped:0 overruns:0 frame:0 
	TX packets:1135 errors:0 dropped:0 overruns:0 carrier:0 
	collisions:0 txqueuelen:0 
	RX bytes:233311 (227.8 KiB) TX bytes:89372 (87.2 KiB) 
	vnet0 Link encap:Ethernet HWaddr FE:54:00:50:58:7E 
	inet6 addr: fe80::fc54:ff:fe50:587e/64 Scope:Link 
	UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 
	RX packets:161 errors:0 dropped:0 overruns:0 frame:0 
	TX packets:3117 errors:0 dropped:0 overruns:0 carrier:0 
	collisions:0 txqueuelen:500 
	RX bytes:15533 (15.1 KiB) TX bytes:263947 (257.7 KiB) 
	vnet1 Link encap:Ethernet HWaddr FE:54:00:B5:1A:19 
	inet6 addr: fe80::fc54:ff:feb5:1a19/64 Scope:Link 
	UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 
	RX packets:56 errors:0 dropped:0 overruns:0 frame:0 
	TX packets:794 errors:0 dropped:0 overruns:0 carrier:0 
	collisions:0 txqueuelen:500 
	RX bytes:8754 (8.5 KiB) TX bytes:42245 (41.2 KiB) 
	5,启动虚拟机ubuntu10.04后配置网卡 
	#cat /etc/network/interface 
	auto lo 
	iface lo inet loopback 
	auto eth0 
	iface eth0 inet static 
	address 172.16.10.100 
	netmask 255.255.255.0 
	gateway 172.16.10.254 
	#/etc/init.d/networking restart 
	启动即可
