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[mininet-discuss] mac address

Bob Lantz rlantz at
Wed Oct 19 17:02:25 PDT 2011

Well, these questions don't seem to be Mininet questions but rather OpenFlow and NOX questions, which can best be answered by reading the OpenFlow spec, papers, and NOX documentation and/or posting to other mailing lists (e.g. openflow-discuss, nox-dev, etc.), but my brief replies are inline.

On Oct 19, 2011, at 3:24 PM, scolfield wrote:

> Hi,
> Thanks for your reply, but I have some doubt yet.
> If we don't need MAC or IP address, how we could identifier or differ one to another openflow switch?

At the controller, switches are usually differentiated by datapath ID (or possibly by OpenFlow connection.)

> The pyswitch example can learn topology of networks?

I am not aware of pyswitch having that functionality - nor does it need it. If I'm not mistaken, topology
discovery in NOX is in other modules such as netapps/topology.

> Such as a corporation architecture when 
> there are hierarchical switches interconnected one to another creating several "layers" of switches,
> at this case, the one openflow controller connected to two distinct switches, can learn which ports 
> to send a ping packets, for example? 

A ping reply is an ICMP echo reply, which is an IP packet, which can be routed to its destination
by whatever means you choose. It would probably be reasonable to originate it from the switch
it came into (and probably the ingress port) rather than some random port on another switch.

> The packet in messages will be forwarded automatically through
> switches until reach a controller?

PACKET_IN messages are OpenFlow messages which are sent from switch to controller.

> --
> scolfield
> On Wed, Oct 19, 2011 at 17:54, Bob Lantz <rlantz at> wrote:
> p.p.s. Step 1 may not be necessary if the packets "to the switch" won't match any other rules and will be forwarded to the controller by default.
> On Oct 19, 2011, at 12:52 PM, Bob Lantz wrote:
>> If you want to use OpenFlow, then using the Linux networking stack to assign a MAC or IP address to a switch port is unnecessary and undesirable.
>> To "assign" a MAC or IP address to the switch, 
>> 1. Use OpenFlow to install a rule to forward packets to whatever "switch" MAC or IP address you like to the controller. 
>> 2. When you want the "switch" to send packets, simply create them with whatever source MAC and source IP you like.
>> To summarize: this is an important design aspect of OpenFlow which needs to be understood.
>> Bob
>> p.s. To perhaps clarify this issue, I think we may wish to change Mininet to raise an error if you attempt to assign an IP or MAC address to a switch.
>> On Oct 19, 2011, at 9:36 AM, scolfield wrote:
>>> Hi,
>>> I created a python script to configure one topology network...
>>> and why can I set the mac address that I need?? For example,
>>> such as:
>>> sw = net.addSwitch( 'switch', ip='', mac='01:36:42:00:00:01')
>>> I'm using Mininet class for this purpose... anybody have any idea, what is wrong?
>>> That mac address that I want to set, don't set correctly,.. 
>>> set another mac address every time..
>>> _______________________________________________
>>> mininet-discuss mailing list
>>> mininet-discuss at

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