Software Defined Networking

Empty Hardware Table of HP 2920

Occasional Contributor

Empty Hardware Table of HP 2920

Dear all,


I would like to ask is any way can I empty the Hardware table of HP 2920 Switch while sending traffic pass through it? I have a testbed like this:

host 1 -------------------- HP 2920 ---------------------- host 2

I also sent UDP traffic from host 1 to host 2, when the switch connected to the controller, it automatically created the rules in H/W table for connecting between hosts. I want to delete these rules and make the connection broken until I install another rule which matches the traffic (the traffic still sends from host 1 to host 2, but host 2 only receives packages when the controller applies the new rules).


I tried to disable then enable the OpenFlow instance, at first the H/W table was empty but after few seconds, the rules were appeared again (I kept sending traffic).


Can I delete all the rules on H/W table? I'm using OpenFlow 1.0 protocol and Opendaylight controller.


Thanks and Best regards.

Frequent Advisor

Re: Empty Hardware Table of HP 2920

Hi Anh,


SDN controllers most of the time  install a few 'default flows' on a switch in order to steal or copy some traffic that the controller then can use to construct a view of the topology of the network. Sometimes also a flow is installed to ensure that packets that are not matched by any other flow in the tables of the switch are forwarded normally. These flows are typically installed by the controller as soon as the openflow instance on the switch is activated and contacts the controller.  It might be that these are the flows that you are seeing.


This type of flows should typically not interfere with whatever you are trying to to do, so there should be no reason to delete them. Deleting them could impact the behaviour of the controller and depending on the controller they might just get reinstalled immediately. If you have any concerns, could you maybe post output of the flows involved? Let me know if this is of any help to you.


Best regards,