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Open vSwitch Lab

#Open vSwitch Lab kaskdaksdkdaks

Get started with Open vSwitch, flows and OpenFlow controllers.

##Pre-reqs

Linux system with OVS installed.

##Setup

Use this script to add a bridge with ports for testing. The interfaces are moved into IP namespaces to isolate them from the main namespace and from each other.

#!/bin/bash

if [ $# -ne 2 ]; then
    echo "usage: $0 port_num ovs_br"
    exit 1
fi

set -xe

port=p$1
ns=ns$1
br=$2
mac=00:00:00:00:00:0$1
ip=10.0.0.${1}/24

ovs-vsctl --may-exist add-br $br
ovs-vsctl add-port $br $port
ovs-vsctl set Interface $port type=internal
ip netns add $ns
ip link set $port netns $ns
ip netns exec $ns ip link set $port address $mac
ip netns exec $ns ip address add $ip dev $port
ip netns exec $ns sysctl -w net.ipv6.conf.${port}.disable_ipv6=1
ip netns exec $ns ip link set $port up

Call script like:

# sh add-port.sh 1 br0
# sh add-port.sh 2 br0

Then the bridge should look like:

# ovs-vsctl show
e3784497-dc8f-432d-9a2c-923148962c73
    Bridge "br0"
        Port "p2"
            Interface "p2"
                type: internal
        Port "br0"
            Interface "br0"
                type: internal
        Port "p1"
            Interface "p1"
                type: internal

##Test 1 - the NORMAL flow

####Test connectivity:

# ip netns exec ns1 ping -c1 10.0.0.2

####Show flows

# ovs-ofctl dump-flows br0
NXST_FLOW reply (xid=0x4):
 cookie=0x0, duration=560.596s, table=0, n_packets=10, n_bytes=828, idle_age=551, priority=0 actions=NORMAL

This flow gets created by default when you create a bridge.. The NORMAL flow causes the bridge to behave like a simple MAC learning switch. It applies to all ports because no in_port was specified and that is like a wildcard for all ports

####Show the mac table

# ovs-appctl fdb/show br0
 port  VLAN  MAC                Age
    1     0  00:00:00:00:00:01    9
    2     0  00:00:00:00:00:02    9

####Delete all flows

# ovs-ofctl del-flows br0

and ping again - it should fail this time.

####Re-add the NORMAL flow

# ovs-ofctl add-flow br0 actions=NORMAL

##Test 2 - forwarding by port numbers

####Delete all flows

# ovs-ofctl del-flows br0

####Find ofport numbers (OpenFlow port numbers)

# ovs-ofctl show br0

####Add the flows

# ovs-ofctl add-flow br0 in_port=1,actions=output:2
# ovs-ofctl add-flow br0 in_port=2,actions=output:1

####Test

# ip netns exec ns1 ping -c1 10.0.0.2

####Test 3 - forward by destination mac address

####Delete all flows

# ovs-ofctl del-flows br0

####Add the flows

# ovs-ofctl add-flow br0 dl_dst=00:00:00:00:00:01,actions=output:1
# ovs-ofctl add-flow br0 dl_dst=00:00:00:00:00:02,actions=output:2
# ovs-ofctl add-flow br0 dl_dst=ff:ff:ff:ff:ff:ff,actions=flood

####Test

# ip netns exec ns1 ping -c1 10.0.0.2

Use dump-flows and watch the packet counters. Wait several minutes for the ARP cache in the namespaces to expire or delete those entries, and ping again. That should cause the broadcast/flood flow to happen on next ping.

##OVS with an external OpenFlow controller

###Setup

Install the Ryu controller from here

####Start Ryu with the sample L2 learning module

$ ryu-manager ryu/ryu/app/simple_switch.py
loading app ryu/ryu/app/simple_switch.py
loading app ryu.controller.ofp_handler
instantiating app ryu/ryu/app/simple_switch.py of SimpleSwitch
instantiating app ryu.controller.ofp_handler of OFPHandler

####Point the test bridge at it

# ovs-vsctl set-controller br0 tcp:127.0.0.1:6633    

####Check there are no flows yet

# ovs-ofctl dump-flows br0
NXST_FLOW reply (xid=0x4):

####Send some data

# ip netns exec ns1 ping -c1 10.0.0.2

####Check that the controller added new flows

# ovs-ofctl dump-flows br0
NXST_FLOW reply (xid=0x4):
 cookie=0x0, duration=5.808s, table=0, n_packets=1, n_bytes=42, idle_age=0, in_port=2,dl_dst=00:00:00:00:00:01 actions=output:1
 cookie=0x0, duration=0.808s, table=0, n_packets=0, n_bytes=0, idle_age=0, in_port=1,dl_dst=00:00:00:00:00:02 actions=output:2

####Check controller console for new log messages

packet in 270705776096578 00:00:00:00:00:01 00:00:00:00:00:02 1
packet in 270705776096578 00:00:00:00:00:02 00:00:00:00:00:01 2
packet in 270705776096578 00:00:00:00:00:01 00:00:00:00:00:02 1

####Study and change the sample code

See here

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