Added new example of multiple controllers.

examples/controllers.py

+#!/usr/bin/python
+
+"""
+This example creates a multi-controller network from
+semi-scratch; note a topo object could also be used and
+would be passed into the Mininet() constructor.
+"""
+
+from mininet.net import Mininet
+from mininet.node import Controller, OVSKernelSwitch
+from mininet.cli import CLI
+from mininet.log import setLogLevel
+
+Switch = OVSKernelSwitch
+
+def addHost( net, N ):
+    "Create host hN and add to net."
+    name = 'h%d' % N
+    ip = '10.0.0.%d' % N
+    return net.addHost( name, ip=ip )
+
+def multiControllerNet():
+
+    net = Mininet( controller=Controller, switch=Switch)
+
+    print "*** Creating controllers"
+    c1 = net.addController( 'c1', port=6633 )
+    c2 = net.addController( 'c2', port=6634 )
+
+    print "*** Creating switches"
+    s1 = net.addSwitch( 's1' )
+    s2 = net.addSwitch( 's2' )
+
+    print "*** Creating hosts"
+    hosts1 = [ addHost( net, n ) for n in 3, 4 ]
+    hosts2 = [ addHost( net, n ) for n in 5, 6 ]
+
+    print "*** Creating links"
+    [ s1.linkTo( h ) for h in hosts1 ]
+    [ s2.linkTo( h ) for h in hosts2 ]
+    s1.linkTo( s2 )
+
+    print "*** Starting network"
+    net.build()
+    [ controller.start() for controller in c1, c2 ]
+    s1.start( [ c1 ] )
+    s2.start( [ c2 ] )
+
+    print "*** Testing network"
+    net.pingAll()
+
+    print "*** Running CLI"
+    CLI( net )
+
+    print "*** Stopping network"
+    net.stop()
+
+if __name__ == '__main__':
+    setLogLevel( 'info' )  # for CLI output
+    multiControllerNet()