OpenDaylight (ODL) is a popular open-source SDN controller framework. To learn more about OpenDaylight, it is helpful to use it to manage an emulated network of virtual switches and virtual hosts. Most people use the Mininet network emulator to create a virtual SDN network for OpenDaylight to control.
In this post, I will show how to set up OpenDaylight to control an emulated Mininet network using OpenFlow 1.3. Because I am using virtual machines, the procedure I use will work the same in all commonly used host systems: Linux, Windows, and Mac OS X.
Using Virtual Machines
In this lab example, I will use two virtual machines. One will run the Mininet emulated network and the other will run the OpenDaylight controller. I will connect both VMs to a host-only network so they can communicate with each other and with programs running on the host computer, such as ssh and the X11 client.
I will use VirtualBox to run the Mininet VM that I downloaded from the mininet project web site, which is the easiest way to experiment with Mininet. The Mininet project team provides an Ubuntu 14.04 LTS VM image with Mininet 2.2.1, Wireshark and OpenFlow dissector tools already installed and ready to use.
I will install and run the OpenDaylight SDN controller on a new VM I create in VirtualBox.
Setting up the OpenDaylight Virtual Machine
To build the OpenDaylight virtual machine, I downloaded the Ubuntu Server ISO image from the ubuntu.com web site. Then I installed it in a new VM in VirtualBox. If you need directions on how to install an ISO disk image in a VirtualBox virtual machine, please see my post about installing Debian in a VirtualBox VM.
Give the virtual machine a descriptive name. I named the virtual machine OpenDaylight. Configure it so it uses two CPUs and 2 GB or RAM. This is the minimum configuration to support OpenDaylight. Then add a host-only network adapter to the VM.
When the VM is powered off, click on the Settings button:
The OpenDaylight virtual machine
In the VM’s VirtualBox network settings, enable two network interfaces. Connect the first network adapter to the NAT interface (which is the default setting) and the second network adapter to the host-only network, vboxnet0.
Connecting network adapter 2 to the host-only network
Configure OpenDaylight VM interfaces
By default, the VM’s first network adapter is attached to the VirtualBox NAT interface and is already configured when the VM boots up. We need to configure the second network adapter, which is attached to the VirtualBox host-only interface vboxnet0.
List all the devices using th ip command:
brian@odl:~$ ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 08:00:27:ec:a9:f1 brd ff:ff:ff:ff:ff:ff
inet 10.0.2.15/24 brd 10.0.2.255 scope global enp0s3
valid_lft forever preferred_lft forever
inet6 fe80::a00:27ff:feec:a9f1/64 scope link
valid_lft forever preferred_lft forever
3: enp0s8: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
link/ether 08:00:27:b0:f6:70 brd ff:ff:ff:ff:ff:ff
brian@odl:~$
Note: starting in 15.10, Ubuntu uses predictable network interface names like enp0s3 and enp0s8, instead of the classic interface names like eth0 and eth1.
We see that interface enp0s8 has no IP address. This is the second network adapter connected to vboxnet0. VirtualBox can assign an IP address on this interface using DHCP if the DCHP client requests it. So, run the following command to set up interface enp0s8:
brian@odl:~$ sudo dhclient enp0s8
Now check the IP address assigned to enp0s8:
brian@odl:~$ ip addr show enp0s8
3: enp0s8: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 08:00:27:b0:f6:70 brd ff:ff:ff:ff:ff:ff
inet 192.168.56.101/24 brd 192.168.56.255 scope global enp0s8
valid_lft forever preferred_lft forever
inet6 fe80::a00:27ff:feb0:f670/64 scope link
valid_lft forever preferred_lft forever
brian@odl:~$
Now we see the VirtualBox DHCP server connected to the host-only network assigned the IP address 192.168.56.101 to this interface. This is the IP address we should use when connecting to any application running on the VM.
On your system the assigned IP address may be different. You may have set up the VirtualBox preferences to use a different network prefix for the host-only network, or may have configured the DHCP server to provide a diferent address range. Also, if any other VMs were started and connected to the host-only network before this VM, then the IP address assigned will be different. If the IP address is different, that’s OK. Just use the address assigned.
Now, configure the interface enp0s8 so it will remain configured after a restart. Edit the /etc/network/interfaces file:
brian@odl:~$ sudo nano /etc/network/interfaces
Add the following lines to the end of the file /etc/network/interfaces:
# the host-only network interface
auto enp0s8
iface enp0s8 inet dhcp
Connect to the OpenDaylight VM using SSH
I like to use a terminal application when working on Virtual Machines. The VirtualBox console window has too many annoying limitations. For example, I cannot cut-and-paste text from my host system onto the VirtualBox console attached to the virtual machine, or vice-versa.
Open a terminal on host computer and login using SSH:
brian@T420:~$ ssh -X brian@192.168.56.101
Now you are connected to the OpenDaylight virtual machine and can see that the host name in the prompt is changed to is odl, which I configured when installing Ubuntu on the VM.
brian@odl:~$
I also enabled X forwarding when I started SSH so I can run X programs on the OpenDaylight VM, although we won’t do that in this tutorial.
Install Java
The OpenDaylight SDN controller is a Java program so install the Java run-time environment with the following command:
$ sudo apt-get update
$ sudo apt-get install default-jre-headless
Set the JAVA_HOME environment variable. Edit the bashrc file
brian@odl:~$ nano ~/.bashrc
Add the following line to the bashrc file:
export JAVA_HOME=/usr/lib/jvm/default-java
Then run the file:
brian@odl:~$ source ~/.bashrc
Install OpenDaylight
Download the OpenDaylight software from the OpenDaylight web site. On a Linux or Mac OS host, we can use the wget command to download the tar file.
brian@odl:~$ wget https://nexus.opendaylight.org/content/groups/public/org/opendaylight/integration/distribution-karaf/0.4.0-Beryllium/distribution-karaf-0.4.0-Beryllium.tar.gz
Install OpenDaylight by extracting the tar file:
brian@odl:~$ tar -xvf distribution-karaf-0.4.0-Beryllium.tar.gz
This creates a folder named distribution-karaf-0.4.0-Beryllium which contains the OpenDaylight software and plugins.
OpenDaylight is packaged in a karaf container. Karaf is a container technology that allows the developers to put all required software in a single distribution folder. This makes it easy to install or re-install OpenDaylight when needed because everything is in one folder. As we will see later, karaf also allows programs to be bundled with optional modules that can be installed when needed.
Start OpenDaylight
To run OpenDaylight, run the karaf command inside the package distribution folder.
brian@odl:~$ cd distribution-karaf-0.4.0-Beryllium
brian@odl:~$ ./bin/karaf
Now the OpenDaylight controller is running.
OpenDaylight running in a virtual machine
Install OpenDaylight features
Next, install the minimum set of features required to test OpenDaylight and the OpenDaylight GUI:
opendaylight-user@root> feature:install odl-restconf odl-l2switch-switch odl-mdsal-apidocs odl-dlux-all
The above is an example of installing optional modules in a karaf container. You only need to install an optional feature once. Once installed, these features are permanently added to the controller and will run every time it starts.
We installed the following features. Click on each feature to learn more about it:
- odl-restconf: Allows access to RESTCONF API
- odl-l2switch-switch: Provides network functionality similar to an Ethernet switch
- odl-mdsal-apidocs: Allows access to Yang API
- odl-dlux-all: OpenDaylight graphical user interface
To list all available optional features, run the command:
opendaylight-user@root> feature:list
To list all installed features, run the command:
opendaylight-user@root> feature:list --installed
Information about OpenDaylight optional features is available on the OpenDaylight wiki.
Stop OpenDaylight
When you want to stop the controller, enter the system:shutdown or logout at the opendaylight-user prompt.
Set up the Mininet Virtual Machine
I do not cover all the steps required to set up the Mininet VM in this post because I already covered that topic in another post: Setting up the Mininet VM.
Start the Mininet VM in the VirtualBox Manager. Now we should have two VMs running: OpenDaylight VM and Mininet VM. If we started the OpenDaylight VM first, it will have IP address 192.168.56.101 and the mininet VM will receive the second available IP address on the host-only network, 192,168.56.102. We can verify this by running the ip command on the Mininet VM console:
mininet@mininet-vm:~$ ip addr show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 08:00:27:e2:98:cc brd ff:ff:ff:ff:ff:ff
inet 192.168.56.102/24 brd 192.168.56.255 scope global eth0
valid_lft forever preferred_lft forever
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 08:00:27:1b:c1:07 brd ff:ff:ff:ff:ff:ff
inet 10.0.2.16/24 brd 10.0.2.255 scope global enp0s3
valid_lft forever preferred_lft forever
mininet@mininet-vm:~$
Note: The Mininet VM is based on Ubuntu Server 14.04, which does not yet use the predictable network interface names like enp0s3 and enp0s8, so we see interface names like eth0 and eth1.
We see eth0 is connected to the host-only interface because it has IP address 192.168.56.102 which is in the address range assigned by the VirtualBox hot-only network DHCP server. So we know we need to use IP address 192.168.56.102 to access applications running on this virtual machine.
Connect to the Mininet VM using SSH
Now open a terminal window on your host computer and SSH into the Mininet VM. Turn X forwarding on. (If you are using Windows, use Xming for an X Window System Server and Putty as an SSH client)
brian@T420:~$ ssh -X 198.168.56.102
Start Mininet
On the Mininet VM, start a simple network topology. In this case, we will do the following:
- Set up three switches in a linear topology
- Each switch will be connected to one host
- The MAC address on each host will be set to a simple number
- The remote controller, OpenDaylight, is at IP address 192.168.56.101:6633
- We will use OpenFlow version 1.3
The Mininet command to start this is:
mininet@mininet-vm:~$ sudo mn --topo linear,3 --mac --controller=remote,ip=192.168.56.101,port=6633 --switch ovs,protocols=OpenFlow13
Test the network
Test that the OpenDaylight controller is working by pinging all nodes. Every host should be able to reach every other host:
mininet> pingall
*** Ping: testing ping reachability
h1 -> h2 h3
h2 -> h1 h3
h3 -> h1 h2
*** Results: 0% dropped (6/6 received)
The OpenDaylight Graphical User Interface
Open a browser on your host system and enter the URL of the OpenDaylight User Interface (DLUX UI). It is running on the OpenDaylight VM so the IP address is 192.168.56.102 and the port, defined by the application, is 8181:
So the URL is: http://192.168.56.101:8181/index.html.
The default username and password are both admin.
Log in to OpenDaylight controller
Topology
Now we see the network topology in the OpenDaylight controller’s topology tab.
Topology of the Mininet network
You can see the network that is emulated by the Mininet network emulator. You may test OpenDaylight functionality by building different network topologies in Mininet with different attributes, and by using OpenDaylight to run experiments on the emulated network. For example, you may break links between switches in Mininet to test how the network responds to faults.
Nodes
Click on the Nodes tab to see information about each switch in the network:
List of nodes
Click on the Node Connectors link in each row to see information about each port on the switch:
Interfaces
Yang UI
Yang is a data modelling structure. Engineers who work with hardware routers and switches will be familiar with another data modeling structure based on SNMP, SMI, and MIB. Yang provides functionality in SDN switches that is analogous to SMI for non-SDN switches.
The OpenDaylight Yang UI is a graphical REST client for building and sending REST requests to the OpenDaylight data store. We can use the Yang UI to get information from the data store, or to build REST commands to modify information in the data store — changing network configurations.
Click on the Yang UI tab. Then click on the Expand all button to see all available APIs. Not all of them will work because we did not install all features. One API that will work is the Inventory API. Click on it, then navigate down to the nodes attribute and click on the Send button to send the GET API method to the controller.
Yang data model of the network
Scroll down to see all the inventory information about the network: nodes, ports, statistics, etc. Click on the switches and interfaces to see the details of each.
Understanding the Yang data model and learning how to read and write to the data store is key to understanding Software Defined Networking with the OpenDaylight controller.
Capturing OpenFlow Messages
To dive deeper into how SDN controllers and switches operate, you may want to view the OpenFlow messages exchanged between the controller and switches in the network.
The Mininet VM comes with Wireshark installed, with a custom version of the OpenFlow dissector already set up.
So the easiest way to view OpenFlow messages is to start Wireshark on the Mininet VM and capture data on the interface connected to the host-only network, which is eth0 in this case.
open a new terminal window and connect to the Mininet VM using SSH with X Forwarding enabled (or use Putty and Xming if you are using Windows):
brian@T420:~$ ssh -X 192.168.56.102
Start Wireshark on the Mininet VM:
mininet@mininet-vm:~$ sudo wireshark &
You will see a warning dialog but you can ignore it. Starting Wireshark with root privileges is a security risk but, for our simple testing, we can ignore that — or you can follow the directions in the warning message to set up Wireshark in a more secure way.
Create a display filter for OpenFlow messages. Enter the text, of in the Filter window and click on Apply. Now you will see only OpenFlow messages in the Wireshark display, as shown below.
Viewing captured OpenFlow messages in Wireshark
Shut down the project
When it is time to end the project, shut down Mininet and OpenDaylight using the following commands:
On the Mininet VM, stop Mininet and clean up the node, then shut down the VM:
mininet> exit
mininet@mininet:~$ sudo mn -c
mininet@mininet:~$ sudo shutdown -h now
On the OpenDaylight VM, stop OpenDaylight and shut down the VM:
opendaylight-user@root> system:shutdown
brian@odl:~$ sudo shutdown -h now
Both VMs should now show that they are stopped in the VirtualBox Manager application.
Conclusion
We showed how to install OpenDaylight in a virtual machine and connect it to the Mininet network emulator running on another virtual machine. We demonstrated some features of OpenDaylight and showed how to capture OpenFlow messages exchanged between the controller and the emulated switches.
