On May 18, 2013, at 4:16 AM, chenli wrote: > But I want to ask why during the connection between OpenFlow switch and POX > controller, POX command line usually dump some information like below: > > [packet ] (dhcp parse) warning DHCP packet data too short to > parse header: data len 86 > > Is this invoke by the arp broadcast or the other problems?
I've added this to the POX manual FAQ under the heading "What are these log messages from the packet subsystem?": https://openflow.stanford.edu/display/ONL/POX+Wiki Generally this is caused by a packet being sent to the controller due to a table miss. Switches usually default to not sending the entire packet -- they only send the first part (often the first 128 bytes). This is enough to see the MAC addresses, ethertype, VLAN, IP header, etc. But it's often NOT enough to, for example, hold an entire DHCP message. Thus, when a DHCP message gets sent to the controller, if POX tries to parse it, it often finds it can't and issues a message like this. Unless you're actually trying to examine the DHCP message, however, this isn't indicative of any problem, which is why the message comes out at INFO level and not WARN level (despite the fact that the message itself contains the word "warning", which is a holdover from long ago). I routinely switch the packet subsystem to warning log level (log.level --packet=WARN). -- Murphy
