xen网络问题的定位思路（网桥模式）

June 20th, 2009

装好xen虚拟机之后，如果网络不通会很恼火不知如何下手，介绍一下我一般碰到这些问题的定位步骤。以下基于suse 10，xen版本应该是3.1。

  1. 检查domU的网卡是否正常，用ifconfig查看mac地址是否和xen配置文件的vif配置相同；ping网卡的ip是否可达。

<pre class=php name=code>linux-cjfq:~ # ifconfig eth0 Link encap:Ethernet HWaddr 00:16:3E:21:C4:F7

cat suse_99.sxp

vif=[ ‘mac=00:16:3e:21:c4:f7’, ]</pre>

  1. 保证dom0是和网络连通的；dom0和domU可以不在一个网段，例如dom0使用10.1.2.0网段，掩码为255.255.255.0，domU使用10.1.3.0网段，掩码为255.255.255.0，dom0和domU之间互相不能ping通，但能和各自网段内的机器通信。

  2. 检查dom0上的虚拟网卡设备是否正常，vif设备的编号和xm list看到的id是对应的； 若domU为半虚拟化，则dom0的ifconfig能看到一个vif的设备：

<pre class=php name=code>vif1.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:79119 errors:0 dropped:0 overruns:0 frame:0 TX packets:325938 errors:0 dropped:113 overruns:0 carrier:0 collisions:0 txqueuelen:32 RX bytes:25527092 (24.3 Mb) TX bytes:136111227 (129.8 Mb) //若domU为半虚拟化，则dom0的ifconfig能看到tap和vif两个设备： tap0 Link encap:Ethernet HWaddr DA:2A:EA:33:2E:B7 inet6 addr: fe80::d82a:eaff:fe33:2eb7/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:521847 errors:0 dropped:0 overruns:0 frame:0 TX packets:3413468 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:500 RX bytes:288369497 (275.0 Mb) TX bytes:468761976 (447.0 Mb) vif11.0 Link encap:Ethernet HWaddr FE:FF:FF:FF:FF:FF inet6 addr: fe80::fcff:ffff:feff:ffff/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:8611878 overruns:0 carrier:0 collisions:0 txqueuelen:32 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)</pre>

  1. 检查dom0上的网桥设置是否正常，通常使用下面几个命令；

<pre class=php name=code>linux-uoiv:/vm # brctl show bridge name bridge id STP enabled interfaces bond0 8000.0018822e2450 no pbond0 vif1.0 //domU的vif网卡是通过pbond0网卡接入网络的，xen虚拟了一个网桥设备bond0，pbond0和vif1.0都接到这个网桥上。 linux-uoiv:~ # /etc/xen/scripts/network-bridge status ============================================================ 8: bond0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc noqueue link/ether 00:18:82:2e:24:50 brd ff:ff:ff:ff:ff:ff inet 192.168.194.133/23 brd 192.168.195.255 scope global bond0 8: bond0: <BROADCAST,MULTICAST,UP,10000> mtu 1500 qdisc noqueue link/ether 00:18:82:2e:24:50 brd ff:ff:ff:ff:ff:ff inet 192.168.194.133/23 brd 192.168.195.255 scope global bond0

bridge name bridge id STP enabled interfaces bond0 8000.0018822e2450 no pbond0 vif1.0

10.1.1.0/24 dev eth3 proto kernel scope link src 10.1.1.72 192.168.194.0/23 dev bond0 proto kernel scope link src 192.168.194.133 169.254.0.0/16 dev eth3 scope link 127.0.0.0/8 dev lo scope link default via 192.168.194.1 dev bond0

Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.1.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth3 192.168.194.0 0.0.0.0 255.255.254.0 U 0 0 0 bond0 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth3 127.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 lo 0.0.0.0 192.168.194.1 0.0.0.0 UG 0 0 0 bond0</pre> 如果有多个网卡，并且不使用eth0作为网桥出口的话，请参考xen启动默认网桥的问题进行配置。

Simon Lee

My blog