linuxrouter.py

#!/usr/bin/python

"""
linuxrouter.py: Example network with Linux IP router
 
This example converts a Node into a router using IP forwarding
already built into Linux.

The topology contains a router with three IP subnets:
 - 192.168.1.0/24 (interface IP: 192.168.1.1)
 - 172.16.0.0/12 (interface IP: 172.16.0.1)
 - 10.0.0.0/8 (interface IP: 10.0.0.1)

 It also contains three hosts, one in each subnet:
 - h1 (IP: 192.168.1.100)
 - h2 (IP: 172.16.0.100)
 - h3 (IP: 10.0.0.100)

"""

from mininet.topo import Topo
from mininet.net import Mininet
from mininet.node import Node
from mininet.log import setLogLevel
from mininet.cli import CLI
from mininet.util import irange

class Router( Node ):
    "A Node with IP forwarding enabled."

    def config( self, **params ):
        super( Router, self).config( **params )
        # Enable forwarding on the router
        self.cmd( 'sysctl net.ipv4.ip_forward=1' )

    def terminate( self ):
        self.cmd( 'sysctl net.ipv4.ip_forward=0' )
        super( Router, self ).terminate()


class NetworkTopo( Topo ):
    "A simple topology of a router with three subnets (one host in each)."

    def build( self, n=2, h=1, **opts ):
        router = self.addNode( 'r0', cls=Router, ip='192.168.1.1/24' )
        h1 = self.addHost( 'h1', ip='192.168.1.100/24', defaultRoute='via 192.168.1.1' )
        h2 = self.addHost( 'h2', ip='172.16.0.100/12', defaultRoute='via 172.16.0.1' )
        h3 = self.addHost( 'h3', ip='10.0.0.100/8', defaultRoute='via 10.0.0.1' )
        self.addLink( h1, router, intfName2='r0-eth1', params2={ 'ip' : '192.168.1.1/24' } )
        self.addLink( h2, router, intfName2='r0-eth2', params2={ 'ip' : '172.16.0.1/12' } )
        self.addLink( h3, router, intfName2='r0-eth3', params2={ 'ip' : '10.0.0.1/8' } )

def run():
    topo = NetworkTopo()
    net = Mininet( topo=topo, controller=None ) # no controller needed
    net.start()
    CLI( net )
    net.stop()

if __name__ == '__main__':
    setLogLevel( 'info' )
    run()