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Software Defined Data Centre lab

This lab creates a software-defined data centre network using spine-leaf architecture built with Open-vSwitch switches.

Requirements

To use this lab, you need to install containerlab on Linux. You also need to have basic familiarity with Docker. This lab uses the following Docker images (they will be pulled automatically when you start the lab):

  • martimy/ryu-flowmanager:latest — includes a Ryu controller and FlowManager.
  • wbitt/network-multitool:alpine-minimal — a Linux with simple tools

How does it work?

This lab builds an SDN using Open vSwitch (OVS) and Docker containers. These components are "glued" together using containerlab.

The Open vSwitch is an open-source virtual switch that is included in many Linux distributions. OVS is designed to work as a standalone switch that supports many standard management interfaces and protocols. OVS can also work as an SDN switch supporting OpenFlow protocol.

As an OpenFlow switch, the OVS needs an SDN controller. The SDN controller used in this lab is Ryu. Ryu is installed in a Docker image along with FlowManager app, which provides a GUI access to the switches.

Hosts in the data center are emulated using a Docker image with pre-installed tools for testing.

Containerlab provides mechanisms to start Docker containers, build virtual topologies, and manage their lifecycle. A lab structure is provided in a YAML file that includes the containers to be deployed and their connections. However, containerlab, cannot create bridges (standard or OVS) other than the management bridge. Therefore, the bridges in this lab must be created externally using a shell script before deploying the containerlab topology. Also, another shell script is required to delete all bridges at the end of the lab.

Starting and ending the lab

You must create the switches first, then deploy the lab:

sudo ./setup-dc.sh
sudo clab deploy -t sdn-dcn.clab.yml

(optional) OVS will assign ports numbers sequentially in the order links are defined in the setup-dc.sh and the sdn-dcn.clab.yml. To ensure port numbers are consistent, you may want to request port number change.

sudo ./num-ports.sh

To end the lab:

sudo clab destroy -t sdn-dcn.clab.yml --cleanup
sudo ./reset-dc.sh

Try this

Check the controller

Confirm that all switches are connected to the controller:

$ sudo ovs-vsctl show
6324bfc8-4c27-4eb1-852d-bc560406943e
    Bridge leaf1
        Controller "tcp:172.10.10.10:6653"
            is_connected: true

<remaining output omitted>

To access the FlowManager GUI, direct your browser to http://172.10.10.10:8080/home/ from your host machine. If the host does not have a desktop or if you want to access it remotely use:

ssh -L 8080:172.10.10.10:8080 -p 2222 user@remotehost

Replace user@remotehost with the username and address of your host machine.

The --observe-links used above, allows the controller to discover the topology using LLDP. The FlowManager manager will show the topology as in the next figure:

IMG1 IMG2

Running an SDN app

Note that the clab runs an app that populate the switchs' flow table by installing flow entries that forward packets between each pair of nodes. The app is loaded in with the flowmanager when the topology is deployed.

To test connectivity, ping from any one host to another:

$ docker exec -it clab-sdn-dcn-h11 ping 192.168.11.3
PING 192.168.11.3 (192.168.11.3) 56(84) bytes of data.
64 bytes from 192.168.11.3: icmp_seq=1 ttl=64 time=0.419 ms
64 bytes from 192.168.11.3: icmp_seq=2 ttl=64 time=0.094 ms
64 bytes from 192.168.11.3: icmp_seq=3 ttl=64 time=0.105 ms
64 bytes from 192.168.11.3: icmp_seq=4 ttl=64 time=0.087 ms
64 bytes from 192.168.11.3: icmp_seq=5 ttl=64 time=0.097 ms
^C
--- 192.168.11.3 ping statistics ---
5 packets transmitted, 5 received, 0% packet loss, time 4090ms
rtt min/avg/max/mdev = 0.087/0.160/0.419/0.129 ms

Observe the change in the flow tables in the switches.

Using Wireshark

You can use Wireshark to monitor traffic on any host interface in the network. For example, if you want to monitor OpenFlow traffic in and of the controller:

sudo ip netns exec clab-sdn-dcn-ctrl tcpdump -U -nni eth0 -w -" | wireshark -k -i -

Or remotely:

>ssh -p 2222 user@remotehost "sudo -S ip netns exec clab-sdn-dcn-ctrl tcpdump -U -nni eth0 -w -" | wireshark -k -i -

Using sFlow

You can enable sFlow by uncommenting the sFlow configuration lines in setup-dc.sh nd sdn-dcn.yml files. This will install/deploy sflowtrend tool, which allows you to view sflow data sent from the switches. Direct you browser to http:/localhost:8087 on the host machine or to access remotely:

ssh -L 8087:172.10.10.100:8087 -p 2222 user@remotehost

Modifying the SDN App

You can change the SDN app that controlles the network by modifying the ENTRYPOINT of the controller image in the YAML topology file:

entrypoint: ryu-manager flowmanager/flowmanager.py <app>

You must destory then deploy the topology again to apply the change (or use docker commands). However, I don't recommed using this lab to develop SDN applications. You may need different environment more sutiable for this purpose.

Useful Links