[pox-dev] l2_learning_tutorial flow rules (strange behavior?)

[Murphy McCauley]

Yes, that's always going to happen with l2_learning_tutorial.  This is, in fact, an example of how NOT to try to write a learning switch, but without proper context.  I deleted it in development fork/branch a while back, but looks like I never did on the master branch.  I have done so now.

The problem you're seeing here was actually just discussed on this list a few days ago.  The issue is that the "learned" rules result in hiding other packets from the controller, so it never learns all the destinations.

If you want a good example of a switch for a tutorial, look at forwarding.l2_pairs or samples.of_tutorial.  l2_pairs gets around the issue of hiding other sources by only installing rules for each PAIR of learned addresses.  These may only be available in the betta (development) branch.

-- Murphy

On Oct 1, 2012, at 11:38 AM, Tmusic wrote:

> Hi,
> 
> I'm trying to learn how to establish flow rules by studying l2_learning_tutorial, but I'm experiencing rather strange behavior.
> 
> On a VM with mininet (one switch, three hosts) and POX installed I first start up mininet and then the l2_learning_tutorial (the behavior is easier to see this way).
> I added one line after the flow installing to see what happens:     print 'added route to', packet.src,'(packet destined to',packet.dst,')'
> 
> When I perform pingall in mininet (one or more), the same routes are added over and over again (see print statement above).
> Dpctl shows that only two entries are being added (I expected three):
> 
>   cookie=0, duration_sec=268s, duration_nsec=529000000s, table_id=0, priority=32768, n_packets=16, n_bytes=1344, idle_timeout=0,hard_timeout=0,
> dl_dst=00:00:00:00:00:02,actions=output:1
>   cookie=0, duration_sec=268s, duration_nsec=463000000s, table_id=0, priority=32768, n_packets=11, n_bytes=910, idle_timeout=0,hard_timeout=0,dl_dst=00:00:00:00:00:03,actions=output:2
> 
> The packets seem to keep going to the controller.
> 
> Any ideas?
> 
> Thank you in advance!
> 
> Tim
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