Connecting two Mininet networks with GRE tunnel – Part 2

Update: Find another post about how I used Linux GRE tunnels to do the same.

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This is a followup to an older post about connecting two MiniNet sessions with a GRE tunnel. I’ve made up some new scripts to help test the functionality plus I’ll provide a little more information on checking if the GRE tunnel is actually registered. The one problem I have run into a few times using Open vSwitch was trying to get the GRE tunnel interface on each switch to register with the controller. If it doesn’t register, then you aren’t going to see any traffic flow across. For this example, both MiniNet sessions will connect to a remote controller. This will also help show if the GRE registered.

The following in the MiniNet python script that you will run on the your first VM.

#!/usr/bin/python

from mininet.net import Mininet
from mininet.node import Controller, RemoteController
from mininet.cli import CLI
from mininet.log import setLogLevel, info

def emptyNet():

    NODE2_IP='192.168.56.103'
    CONTROLLER_IP='192.168.56.103'

    net = Mininet( topo=None,
                   build=False)

    net.addController( 'c0',
                      controller=RemoteController,
                      ip=CONTROLLER_IP,
                      port=6633)

    h1 = net.addHost( 'h1', ip='10.0.0.1' )
    h2 = net.addHost( 'h2', ip='10.0.0.2' )
    s1 = net.addSwitch( 's1' )
    net.addLink( h1, s1 )
    net.addLink( h2, s1 )
    net.start()

    # Configure the GRE tunnel
    s1.cmd('ovs-vsctl add-port s1 s1-gre1 -- set interface s1-gre1 type=gre options:remote_ip='+NODE2_IP)
    s1.cmdPrint('ovs-vsctl show')

    CLI( net )
    net.stop()

if __name__ == '__main__':
    setLogLevel( 'info' )
    emptyNet()

This next MiniNet python script will be run on another VM.

#!/usr/bin/python

from mininet.net import Mininet
from mininet.node import Controller, RemoteController
from mininet.cli import CLI
from mininet.log import setLogLevel, info

def emptyNet():

    NODE1_IP='192.168.56.102'
    CONTROLLER_IP='192.168.56.103'

    net = Mininet( topo=None,
                   build=False)

    net.addController( 'c0',
                      controller=RemoteController,
                      ip=CONTROLLER_IP,
                      port=6633)

    h3 = net.addHost( 'h3', ip='10.0.0.3' )
    h4 = net.addHost( 'h4', ip='10.0.0.4' )
    s2 = net.addSwitch( 's2' )
    net.addLink( h3, s2 )
    net.addLink( h4, s2 )
    net.start()

    # Configure the GRE tunnel
    s2.cmd('ovs-vsctl add-port s2 s2-gre1 -- set interface s2-gre1 type=gre options:remote_ip='+NODE1_IP)
    s2.cmdPrint('ovs-vsctl show')

    CLI( net )
    net.stop()

if __name__ == '__main__':
    setLogLevel( 'info' )
    emptyNet()

You will need to modify the scripts to set the IP addresses at the top to the appropriate values for your environment. Once the scripts are ready, we’ll start them up. Don’t worry about the message about not being able to contact the controller. We’ll start it up after. Also, I’ve configured the scripts to automatically create the GRE tunnel to the other MiniNets.

On VM1.

mininet@mininet21:~$ sudo ./greTest-1.py
Unable to contact the remote controller at 192.168.56.103:6633
*** Configuring hosts
h1 h2
*** Starting controller
*** Starting 1 switches
s1
*** s1 : ('ovs-vsctl show',)
007a537b-9138-4ee9-b0dd-77182c3b4cea
    Bridge "s1"
        Controller "tcp:192.168.56.103:6633"
        fail_mode: secure
        Port "s1-eth1"
            Interface "s1-eth1"
        Port "s1-eth2"
            Interface "s1-eth2"
        Port "s1-gre1"
            Interface "s1-gre1"
                type: gre
                options: {remote_ip="192.168.56.103"}
        Port "s1"
            Interface "s1"
                type: internal
    ovs_version: "1.4.0+build0"
*** Starting CLI:
mininet>

On VM2:

mininet@mininet21:~$ sudo ./greTest-2.py
*** Configuring hosts
h3 h4
*** Starting controller
*** Starting 1 switches
s2
*** s2 : ('ovs-vsctl show',)
ef39063c-46be-44e3-b89c-faaf7ffcf351
    Bridge "s2"
        Controller "tcp:192.168.56.103:6633"
        fail_mode: secure
        Port "s2-gre1"
            Interface "s2-gre1"
                type: gre
                options: {remote_ip="192.168.56.102"}
        Port "s2-eth1"
            Interface "s2-eth1"
        Port "s2-eth2"
            Interface "s2-eth2"
        Port "s2"
            Interface "s2"
                type: internal
    ovs_version: "1.4.0+build0"
*** Starting CLI:
mininet>

Now start the controller. For this test, I’m just going to use the OpenFlow reference controller.

mininet@mininet21:~$ controller -v ptcp:6633

The above will start printing a lot of messages as soon at the switches start connecting to the controller. But here is where you want to watch closely as the switches register. You want to look for the following message.

Jan 20 21:24:10|00009|vconn|DBG|tcp:192.168.56.102:41173: received: features_reply (xid=0x9ba82531): ver:0x1, dpid:1
n_tables:255, n_buffers:256
features: capabilities:0xc7, actions:0xfff
 1(s1-eth1): addr:ca:06:71:62:79:85, config: 0, state:0
     current:    10GB-FD COPPER
 2(s1-eth2): addr:72:89:9d:be:6f:1f, config: 0, state:0
     current:    10GB-FD COPPER
 3(s1-gre1): addr:fe:d4:30:b3:b9:e0, config: 0, state:0
 LOCAL(s1): addr:9a:a3:5c:e3:01:40, config: 0x1, state:0x1

Jan 20 21:24:11|00017|vconn|DBG|tcp:192.168.56.103:36309: received: features_reply (xid=0x9a4c5b0d): ver:0x1, dpid:2
n_tables:255, n_buffers:256
features: capabilities:0xc7, actions:0xfff
 1(s2-eth1): addr:72:52:76:ea:d6:90, config: 0, state:0
     current:    10GB-FD COPPER
 2(s2-eth2): addr:d2:80:1b:4b:89:43, config: 0, state:0
     current:    10GB-FD COPPER
 3(s2-gre1): addr:6e:ad:4b:5c:e6:be, config: 0, state:0
 LOCAL(s2): addr:ae:49:99:96:c7:4e, config: 0x1, state:0x1

The above two messages that got printed out are what is important. Make sure you see your GRE interface listed for each switch. If it isn’t there, then something is wrong with your configuration or with the Open vSwitch that you have installed. If all looks good, then the last step is to verify with some traffic.

In MiniNet on VM1:

mininet> h1 ping -c 1 10.0.0.3
PING 10.0.0.3 (10.0.0.3) 56(84) bytes of data.
64 bytes from 10.0.0.3: icmp_req=1 ttl=64 time=0.613 ms

--- 10.0.0.3 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.613/0.613/0.613/0.000 ms

There you go. I sent a ping from h1 on VM1 to h3 on VM2 over the GRE tunnel. In the above example I use the reference controller. You can use whatever controller you wish and it might give you more details on the interfaces and connection. Just update the CONTROLLER_IP with the IP address where your controller is running.

Hope these new scripts and extra info help you in your journey.

This post ‘Connecting two Mininet networks with GRE tunnel – Part 2’ first appeared on https://gregorygee.wordpress.com/.