2. INTRODUCTION TO MININET
Mininet
A network emulator which creates realistic virtual network
Runs real kernel, switch and application code on a single machine
Provides both Command Line Interface (CLI) and Application Programming Interface (API)
• CLI: interactive commanding
• API: automation
Abstraction
• Host: emulated as an OS level process
• Switch: emulated by using software-based switch
• E.g., Open vSwitch, SoftSwitch
2
4. FLOW OF THE LAB
Download the virtual machine
Setup the virtual machine
Check the setup in Linux
Create the network
Examine the network
Work with basic OpenFlow commands
Add a controller
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5. DOWNLOAD THE VIRTUAL MACHINE
For this lab a virtual machine appliance in ovf format must be
downloaded from the OpenFlow Tutorial website here
https://github.com/downloads/mininet/mininet/mininet-2.0.0-113012-amd64-ovf.zip
Download this file
Expand the zip file
You should see these files
5
6. SETUP THE VIRTUAL MACHINE
To import this appliance into VirtualBox
Select
File
Import Appliance
Select the ovf image
Press the Import button
This lab requires two virtual NICs
The first one should be set to host-only network
The second one to NAT
6
7. CHECK LINUX
Mininet is a command line tool that runs in Linux
The Mininet prompt looks like this
mininet>
The Linux prompt ends with a $ for a normal user
It ends in # for the root account
We will use the sudo command to run the Linux commands with root
privileges at the normal user prompt
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8. LOGIN VM
Start the virtual machine
Login to Linux
The login is
mininet
mininet
The screen should look like this
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10. VM NETWORK CONFIGURATION
Let’s see if the two network interfaces are setup correctly
At the Linux prompt enter
ifconfig
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11. VM NETWORK CONFIGURATION
Three interfaces should appear
Two physical interfaces called
eth0
eth1
And the loopback interface
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12. VM NETWORK CONFIGURATION
One of the physical interfaces should have a 192 address and the
other a 10 address
We will access the virtual machine using a terminal program using the
192 address
If either of the eth Ethernet interfaces are missing, run this command
sudo dhclient ethx
Where the x in ethx is the number of the interface
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14. SET UP NETWORK ACCESS
As you can see the eth1 interface is missing
After the dhclient command is run this appears
sudo dhclient ethx
Where the x in ethx is the number of the interface
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16. The tutorial VM is shipped without a desktop environment, to reduce its size. All
the exercises will be done through X forwarding, where programs display graphics
through an X server running on the host OS.
Open a terminal (Terminal.app in Mac, Gnome terminal in Ubuntu, etc). In that
terminal, run:
$ ssh -X [user]@[Guest IP Here]
Replace [user] with the correct user name for your VM image.
Replace [Guest] with the IP you just noted.
If ssh does not connect, make sure that you can ping the IP address you are connecting to.
ACCESS VM VIA SSH
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17. To not use X11 and log in to the VM console window - not via an ssh
session!
Install GUI
Login VM, and type:
$ sudo apt-get update && sudo apt-get install xinit lxde virtualbox-guest-dkms
At this point, you should be able to start an X11 session in the VM
console window by typing:
$ startx
ALTERNATIVE: RUN A GUI IN THE VM CONSOLE
WINDOW
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18. MININET TUTORIAL
Mininet Command Line Interface Usage
Interact with hosts and switches
• Start a minimal topology
The default run of Mininet sudo mn will create a topology consisting of one controller (c0), one switc
h (s1) and two hosts (h1 and h2).
• Display nodes
• Display links
• Dump information about all nodes
• Exit Mininet:
$ sudo mn
mininet> nodes
mininet> net
mininet> dump
The switches generated with Mininet will
be just simple forwarding devices, without
any "brain" of their own (no control plane)
mininet> exit
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19. To help you start up, here are the most important options for running Mininet:
--topo=TOPO represents the topology of the virtual network, where TOPO could
be:
minimal - this is the default topology with 1 switch and 2 hosts
single,X - a single switch with X hosts attached to it
linear,X - creates X switches connected in a linear/daisy-chain fashion, each switch with one
host attached
tree,X,Y - a tree topology with X depth, Y fanout
--switch=SWITCH creates different type of switches, such as:
ovsk - this is the default Open vSwitch that comes preinstalled in the VM
user - this is a switch running in software namespace (much slower)
MININET TUTORIAL
19
20. --controller=CONTROLLER where CONTROLLER can be:
ovsc - this creates the default OVS Controller that comes preinstalled in the VM
nox - this creates the well-known NOX controller
remote - does not create a controller but instead listens for connections from
external controllers
--mac set easy-to-read MAC addresses for the devices
For more information
$ mn help
MININET TUTORIAL
20
21. Display Mininet Command Line Interface (CLI) commands:
mininet> help
Display nodes:
mininet> nodes
If the first string of the CLI command is a host, switch or controller name, the
command is executed on that node. For instance, to show the interface of host
h1:
mininet> h1 ifconfig
Test connectivity between hosts. For example, test the connectivity between h1
and h2:
mininet> h1 ping h2
Alternatively, you can test the connectivity between all hosts by typing:
mininet> pingall
Exit Mininet:
mininet> exit
Clean up: After every exit do cleanup
$ sudo mn -c
MORE COMMANDS
21
25. sudo mn --link tc,bw=20,delay=20ms
Take a moment to think about our current, very basic,
topology.
(h1)-----20ms-----(s1)-----20ms-----(h2)
Q: When you send a ping, you measure the roundtrip delay for
an ICMP packet to travel from one host to another. Assuming
our current deployment, what will be the reported roundtrip
delay?
EXAMPLE
25
26. A1: ~80 ms
Let’s test that assertion!
mininet> h1 ping -c 8 h2
EXAMPLE (CONT..)
26
27. Do not confuse the dpctl with a controller (it's not the same thing) -
dpctl is just a management/monitoring utility!
SIMPLE EXERCISE
Use ovs-oftcl instead of dpctl
for open vSwitch when running
a controller
In this scenario we have no
remote controller running
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28. STEP 1: Start Mininet with a single switch (the default, Open vSwitch =
ovsk) and 3 hosts:
mininet@mininet-vm:~$ sudo mn --topo=single,3 --mac --switch=ovsk --
controller=remote
EXERCISE (CONT..)
This message: "Unable to contact the remote
controller at 127.0.0.1:6633". This is because,
for the time being, we are going to use mininet
without any controller
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29. In order to double-check that everything started correctly, use the
following mininet commands:
nodes - to list all virtual devices in the topology
net - to list of links between them
dump - to see more info about the hosts
EXERCISE (CONT..)
29
30. STEP 2: Open terminals for each host and run tcpdump on each:
Attention: for Windows/MAC users, make sure you installed & run Xming/XQuartz,
plus you enabled X-forwarding if you are using ssh session to the Mininet VM!
> xterm h1 h2 h3
In the xterms for h2 and h3, run tcpdump, a utility to print the packets seen by a
host:
# tcpdump -XX -n -i h2-eth0
and respectively:
# tcpdump -XX -n -i h3-eth0
In the xterm for h1, send a ping:
# ping -c1 10.0.0.2
EXERCISE (CONT..)
30
31. STEP 3: Test connectivity between h1 and h2: on host h1 perform a
ping -c3 10.0.0.2 (the IP address of host h2)
EXERCISE (CONT..)
31
32. Results:
ping will fail, because the switch does NOT know what to do with
such traffic (and remember, we don't run any controller)
EXERCISE (CONT..)
32
33. Checking the list of flows on the switch (with command dpctl dump-
flows) will show an empty list (again, nobody told the switch how to
deal with the traffic)
CHECKING FLOW RULES
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34. Open new terminal window or create a second SSH window, if you
don't already have one, and run:
$ dpctl show tcp:127.0.0.1:6634
The 'show' command connects to the switch and dumps out its port
state and capabilities.
$ dpctl dump-flows tcp:127.0.0.1:6634
Since we haven't started any controller yet, the flow-table should be
empty.
CHECKING FLOW RULES
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35. STEP 4: Manually add flows on the switch to allow connectivity
between h1 and h2
Use the dpctl add-flow utility to manually install flows on the switch
that will allow connectivity between host h1 and host h2.
$ dpctl add-flow tcp:127.0.0.1:6634 in_port=1,actions=output:2
everything received on port 1 (in_port) send out on port 2
$ dpctl add-flow tcp:127.0.0.1:6634 in_port=2,actions=output:1
everything received on port 2 (return traffic) send out on port 1
ADDING FLOW RULES
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37. Result:
ping is successful
tcpdump on host h2 shows the traffic from/to h1 (ARP and ICMP)
tcpdump on host h3 does not see anything (not even the ARP which
should be broadcast)!
FLOW RULES
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38. ACTIVATE WIRESHARK
Start Wireshark as a background process
$sudo wireshark $
Click on OK to clear any error messages
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39. OBSERVE SDN TRAFFIC
Start a capture in Wireshark using the loopback interface
Create and apply a filter for just the OpenFlow traffic by entering a
display filter in Wireshark using the string
of
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40. LOAD THE CONTROLLER
To generate some traffic we will load a controller as that is the next
step anyway
There are a number of software based or hardware based controllers
that can be used in an SDN
In this example we will load the POX controller
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41. LOAD THE CONTROLLER
To start POX enter these commands
$cd pox
./pox.py forwarding.l2_learning
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45. GUI - Automatic Creation of Mininet Scripts
Visual Network Description - VND (http://www.ramonfontes.com/vnd) - A GUI tool
that allows automatic creation of Mininet and Openflow Controllers Scripts.
GUI - MiniEdit
Included in Mininet in the examples/ directory. miniedit.py
MININET APPS
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46. The MiniEdit script is located in Mininet’s examples folder.
To run MiniEdit, execute the command:
$ sudo ~/mininet/examples/miniedit.py
Mininet needs to run with root privileges so start MiniEdit using the
sudo command.
START MINIEDIT
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49. Right-click on each controller and select Properties from the menu
that appears.
The default port number for each controller is 6633.
Change this so the port numbers used by controllers c0, c1, and c2 are 6633, 6634,
and 6635, respectively.
CONFIGURE THE CONTROLLERS
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51. To set MiniEdit preferences, Edit → Preferences. In the dialogue box
that appears, make the changes you need.
SET MINIEDIT PREFERENCES
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52. Set the Start CLI option
SET MINIEDIT PREFERENCES
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53. SAVE THE CONFIGURATION
Save topology file
To save the Mininet Topology (*.mn) file, click on File in the top menu
bar and select Save from the drop-down menu. Type in a file name
and save the file.
Save custom Mininet script
To save the Mininet Custom Topology (*.py) file, click on File in the
top menu bar and select Save Level 2 Script from the drop-down
menu. Type in the file name and save the file.
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54. To start the simulation scenario, click the Run button on the MiniEdit
GUI
RUN THE MINIEDIT NETWORK SCENARIO
In the terminal window from which
you started MiniEdit, you will see
some messages showing the
progress of the simulation startup and
then the Miniedit CLI prompt
(because we checked Start CLI box in
the MiniEdit preferences window).
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57. First change the userid from root to mininet
# su mininet
Then, check the flow table on switch s1 using the commands below.
It should be empty.
$ sudo ovs-ofctl dump-flows s1
CONT..
57
58. Open a xterm window on hosts h1 and h8. Right-click on each host in
the MiniEdit GUI and select Terminal from the menu that appears.
In the h1 xterm window, start a Wireshark with the command, wireshark &.
In the h8 xterm window, start a packet trace with the command tcpdump.
$ tcpdump –n –i h8-eth0
Run a ping command to send traffic between host h1 and h8
mininet> h1 ping h8
RUN PROGRAMS TO GENERATE AND MONITOR
TRAFFIC
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60. Right-click on link. Choose Link Down from the menu that appears
SIMULATE A BROKEN LINK
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61. Ping again
no more traffic is received at host h8 and that the ping command shows packets
sent from host h1 are not being responded to
Restore the link by choosing Link Up
Check flow tables
$ sudo ovs-ofctl dump-flows s1
CONT..
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62. Quit Wireshark and tcpdump on hosts h1 and h8.
Quit the ping command in the MiniEdit console window by pressing
Ctrl-C on the keyboard.
Then, quit the Mininet CLI by typing exit at the mininet> prompt.
Now, press the Stop button on the MiniEdit GUI.
STOP THE SIMULATION
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63. $ cd ~/mininet/<filepath>
$ sudo chmod 777 <filename>.py
$ sudo ./<filename>.py
RUN A SAVED MININET CUSTOM TOPOLOGY
SCRIPT
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64. Open web browser and go to http://www.ramonfontes.com/vnd/#
VISUAL NETWORK DESCRIPTION(VND)
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65. Create the following topology using drag/drop
CREATE A CUSTOM NETWORK TOPOLOGY
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69. Using the l2_multi pox controller module to find the shortest path
from sender to receiver to send packets.
Run the l2_multi pox controller.
Use discovery module to construct the network topology.
When the topology is known, the l2_multi can use Floyd-Warshall
algorithm to find a shortest path.
Note l2_multi.py is under /pox/pox/forwarding and discovery.py is
under /pox/pox/openflow
RUN CONTROLLER
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73. There are two paths from h1 to h2, i.e.
h1->s3->s4->h2
h1->s3->s5->s6->s4->h4.
The shortest path is h1->s3->s4->h2.
Check the rules for s3 (we can see the rules for arp and ip operations
between 10.0.0.1 (h1) and 10.0.0.2(h2))
CONT..
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79. 79
Switching hubs have a variety of functions
Learns the MAC address of the host connected to a port and retains it in the MAC
address table.
When receiving packets addressed to a host already learned, transfers them to the
port connected to the host.
When receiving packets addressed to an unknown host, performs flooding.
SWITCHING HUB
90. Execute ping from host 1 to host 2
mininet> h1 ping –c 1 h2
Before executing the ping command, execute the tcpdump command so that it is
possible to check what packets were received by each host.
CONFIRMING OPERATION
90
