[pox-dev] l2_learning flow installation

[Murphy McCauley]

On May 27, 2015, at 2:29 PM, Adam Pavlidis <adampavlidis at gmail.com> wrote:

>>> Are you using l2_learning and only l2_learning?
>>>  
>>> I am using  l2_learning, log.level with --DEBUG flag, and a custom module that only handles Flow Removed events (only to print them)
>>> 
>>> 
>>> 
>>> Are you sure?  Try monitoring the OpenFlow connection to the controller (this can be done with Wireshark, for example, or with a little modification to POX).  Do you see packet-ins with the ARPs in them?
>>> 
>>> Sorry you are right, by using Wireshark with OF dissector i see the packet In messages containing arp. 
>>> However, since the hosts don't exchange ARP Messages, but POX receives Packet In messages were do these messages come from? 
>>> Also,
>>> why the ARP request packets encapsulated in Packet In target a specific
>>> MAC, as opposed to usual ARP request targeting every MAC? Is it a 
>>> "keep-alive" like mechanism for ARP Cache entries, or am i way off base?
>> 
>> Are you sure they're not?  You've inspected the right interfaces with Wireshark or whatever?  I am guessing they are there.  (And that Linux's ARP logic is not as straightforward as one might imagine.)
> 
> Well i was certain initially, but now i have some doubts that i did not do something wrong in tcpdump. Now that i used wireshark not only to dissect the OF messages but to inspect the OF Bridge interfaces i was proved wrong again...
> I guess i got carried away by me expectation not to sent/receive messages for a host with an already known MAC and perhaps i terminated the capture prematurely.
> Seems like this is a Linux ARP logic matter as you said. I will search further on that direction.

If you find a nice reference on the ARP logic used, let me know.  I'm always telling people it's not as simple as they think, but never have anything good to point them at. :)  (For the record, the only reason I know this is because I saw it so often due to working on POX!)

> Sorry for bothering you with this, and thanks again for all your help

-- Murphy
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