实验2:Open vSwitch虚拟交换机实践
一、基础要求
1.ovs-vsctl基础操作实践
2.Mininet搭建的SDN拓扑
3.建立流表
4.连通性测试
二、进阶要求
代码
#!/usr/bin/python
from mininet.net import Mininet
from mininet.node import Node
from mininet.link import TCLink
from mininet.log import setLogLevel, info
def myNet():
"Create network from scratch using Open vSwitch."
info( "*** Creating nodes\n" )
s1 = Node( 's1', inNamespace=False )
s2 = Node( 's2', inNamespace=False )
h2 = Node( 'h2' )
h1 = Node( 'h1' )
h3 = Node( 'h3' )
h4 = Node( 'h4' )
info( "s1,s2,h1,h2,h3,h4" )
info( "*** Creating links\n" )
linkopts0=dict(bw=100, delay='1ms', loss=0)
linkopts1=dict(bw=1, delay='100ms', loss=0)
TCLink( s1, h1, **linkopts0)
TCLink( s1, h2, **linkopts0)
TCLink( s2, h3, **linkopts0)
TCLink( s2, h4, **linkopts0)
TCLink( s1, s2, **linkopts1)
info( "(s1,h1),(s1,h2),(s1,s2),(s2,h3),(s2,h4)" )
info( "*** Configuring hosts\n" )
h1.setIP( '192.168.123.1/24' )
info( "h1:192.168.123.1/24\n" )
h2.setIP( '192.168.123.2/24' )
info( "h2:192.168.123.2/24\n" )
h3.setIP( '192.168.123.3/24' )
info( "h3:192.168.123.3/24\n" )
h4.setIP( '192.168.123.4/24' )
info( "h4:192.168.123.4/24\n" )
info( "*** Starting network using Open vSwitch\n" )
s1.cmd( 'ovs-vsctl del-br port1' )
s1.cmd( 'ovs-vsctl add-br port1' )
s2.cmd( 'ovs-vsctl del-br port2' )
s2.cmd( 'ovs-vsctl add-br port2' )
for intf in s1.intfs.values():
intf
s1.cmd( 'ovs-vsctl add-port port1 %s' % intf )
for intf in s2.intfs.values():
intf
s2.cmd( 'ovs-vsctl add-port port2 %s' % intf )
s1.cmd( 'ovs-ofctl -O OpenFlow13 add-flow port1 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4096-\>vlan_vid,output:3' )
s1.cmd( 'ovs-ofctl -O OpenFlow13 add-flow port1 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4097-\>vlan_vid,output:3' )
s1.cmd( 'ovs-ofctl -O OpenFlow13 add-flow port1 priority=1,dl_vlan=0,actions=pop_vlan,output:1' )
s1.cmd( 'ovs-ofctl -O OpenFlow13 add-flow port1 priority=1,dl_vlan=1,actions=pop_vlan,output:2' )
s2.cmd( 'ovs-ofctl -O OpenFlow13 add-flow port2 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4096-\>vlan_vid,output:3' )
s2.cmd( 'ovs-ofctl -O OpenFlow13 add-flow port2 priority=1,in_port=1,actions=push_vlan:0x8100,set_field:4097-\>vlan_vid,output:3' )
s2.cmd( 'ovs-ofctl -O OpenFlow13 add-flow port2 priority=1,dl_vlan=0,actions=pop_vlan,output:1' )
s2.cmd( 'ovs-ofctl -O OpenFlow13 add-flow port2 priority=1,dl_vlan=1,actions=pop_vlan,output:2' )
info( "*** Running test\n" )
h1.cmdPrint( 'ping -Q 0x20 -c 3 ' + h3.IP() )
h1.cmdPrint( 'ping -Q 0x30 -c 3 ' + h4.IP() )
h2.cmdPrint( 'ping -Q 0x30 -c 3 ' + h3.IP() )
h2.cmdPrint( 'ping -Q 0x30 -c 3 ' + h4.IP() )
info( "*** Stopping network\n" )
s1.cmd( 'ovs-vsctl del-br port0' )
s1.cmd( 'ovs-vsctl del-br port1' )
s1.deleteIntfs()
s2.cmd( 'ovs-vsctl del-br port0' )
s2.cmd( 'ovs-vsctl del-br port1' )
s2.deleteIntfs()
info( '\n' )
if __name__ == '__main__':
setLogLevel( 'info' )
info( '*** Scratch network demo (kernel datapath)\n' )
Mininet.init()
myNet()
运行结果
三、个人总结
1.个人感想
基础实验的材料有个小坑:在PPT建立流表的命令行中,因为排版问题把一行代码翻成两行显示,就算CtrlC到终端也会被拆成两行,搞得我照着这一行代码查了半天的问题(因为网上的shell命令多行每行都以$开头,否则默认为1行一句)。其他步骤都到没什么难度
进阶实验的材料中的代码,原作者在设备的cmd前都加了一个print,虽然这个在编译器中会产生语法报错,但实际运行好像不受影响,不过为了美观还是删掉了。
2.问题分享
(1).退出Mininet导致流表找不到设备
在作下发流表的时候,可能存在找不到。这个原因是因为我们用python搭建的设备没有运行在后台,这里需要用到两个终端,一个开着Mininet加载的Python拓扑,另一个用来下发流表
(2).进阶实验修正代码后
进阶实验中可能会存在出现python命令导入文件失败的问题,最后的提示是Filed exists。
- 这里一般有两种情况,
- 第一个是前面的基础实验拓扑没有exit或者Ctrl+C强制挂起,导致内存中存在同名的设备(因为两个实验都是s1、s2)
- 第二个是可能进阶实验的代码上一次运行的时候出问题,因为python边解释边运行的原因,导致全面没问题的代码以及建立在内存中