[SNMP4J] V2 Trap Packet Fragmentation

[Amol Rao]

I see the following exception when trap is being sent out. Any pointers?


java.lang.NullPointerException
        at org.snmp4j.PDU.getBERPayloadLengthPDU(PDU.java:499)
        at org.snmp4j.PDU.getBERLength(PDU.java:436)
        at org.snmp4j.mp.MPv2c.prepareOutgoingMessage(MPv2c.java:118)
        at org.snmp4j.MessageDispatcherImpl.sendPdu(MessageDispatcherImpl.java:444)
        at org.snmp4j.Snmp.sendMessage(Snmp.java:1078)
        at org.snmp4j.Snmp.send(Snmp.java:878)
        at org.snmp4j.Snmp.send(Snmp.java:871)
        at org.snmp4j.Snmp.send(Snmp.java:836)
        at org.snmp4j.Snmp.notify(Snmp.java:780)


Cheers,
Amol

On Mon, Apr 16, 2012 at 1:05 PM, Amol Rao <xamolrao at gmail.com> wrote:
> Hi All:
>  Just wanted to reach out and see if anyone encountered this situation.
>
> I am sending out an SNMP trap (~1K size) from an agent system. When
> manager receives the trap, its observe that its divided into multiple
> traps and each trap carries one variable binding - which leads to
> conclusion that the packets are getting fragmented at the SNMP level,
> I wonder why this happens.
>
> I did wireshark and realized that there is no UDP level fragmentation.
>
> Both source (trap generation) and Destination (trap receiver) uses
> snmp4j-1.11.jar but since on the receiving side, I have logic that
> expects the trap to come in as one UDP packets, the whole thing breaks
> apart. Moreover, I observed that its happening on only one system, the
> same code works on another identical system.
>
> Any pointers as to why this could be happening and what is the way around?
>
> I am pretty sure that we are not crossing UDP packet limit, not that
> it would matter at SNMP layer.
>
> Thanks.
>
> Cheers,
> Amol