Running Open vSwitch in Network Namespace with In-Band Controller

In a previous post, I started the experiment on running Open vSwitch in a network namespace.  I had three scenarios I was trying to accomplish.

1. OVS in each network namespace running in standalone mode (standard L2 learning switch not under SDN control).
2. OVS in each network namespace running in secure mode with a local SDN controller for each switch
3. OVS in each network namespace running in secure mode with a remote in-band SDN controller

In the last post I walked through the first two scenarios but I mentioned I was stuck getting the in-band controller scenario to work. Turns out that the problem I was having was just a simple IP MASK misconfiguration. I had kept thinking of the internal bridge interface (s1 and s2) as being like layer 3 Loopback interface on a router and putting a /32 prefix on them. I realized recently that these are actually an SVI/VLAN interface. Not sure why I got those mixed up. So once I used the correct IP prefix to match the subnet of the network, all worked as planned. So the following are the steps I took to get the last scenario to work.

This script(createBrSdn) creates the bridge in secure mode and adds the ports. Set the controller IP address to the host that will run the controller. In my case, the controller will be running on host h1 which has an IP address of 10.0.0.1/8.

#!/bin/bash

echo Configure OVS for $1
ovs-vsctl --db=unix:/tmp/mininet-$1/db.sock add-br $1
ovs-vsctl --db=unix:/tmp/mininet-$1/db.sock add-port $1 $1-eth0
ovs-vsctl --db=unix:/tmp/mininet-$1/db.sock add-port $1 $1-eth1
ovs-vsctl --db=unix:/tmp/mininet-$1/db.sock set-fail-mode $1 secure
ovs-vsctl --db=unix:/tmp/mininet-$1/db.sock set-controller $1 tcp:10.0.0.1:6633
ovs-vsctl --db=unix:/tmp/mininet-$1/db.sock show

With the script setup, I followed the same instruction I had before but also set the IP address for each of the internal bridge interfaces. So first step was to start the Mininet script and then open XTerms to h1, s1, and s2.

In the xterm for h1 controller:

controller -v ptcp:6633

In the xterm for S1:

startOvsDb s1
startOvs s1
createBrSdn s1
ifconfig s1 inet 10.0.0.100/8

In the xterm for S2:

startOvsDb s2
startOvs s2
createBrSdn s2
ifconfig s2 inet 10.0.0.101/8

Once that was all setup, I could easily get the two hosts to ping each other.

mininet> h1 ping -c 2 h2
PING 10.0.0.2 (10.0.0.2) 56(84) bytes of data.
64 bytes from 10.0.0.2: icmp_req=1 ttl=64 time=2.52 ms
64 bytes from 10.0.0.2: icmp_req=2 ttl=64 time=1.50 ms

--- 10.0.0.2 ping statistics ---
2 packets transmitted, 2 received, 0% packet loss, time 1001ms
rtt min/avg/max/mdev = 1.502/2.015/2.529/0.515 ms

I’m glad all this finally worked out. I think I might now try and wrap all this into a Mininet custom switch class so people can try their own experiments at using in-band conntroller.

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