WinSNMP v1traps

Question

I'm using WinSNMP in c++ to send snmp traps. For backwards compatibility I’m required to send v1 snmp traps. WinSNMP works with v2 traps but is capable of converting those v2 traps to v1 when sending the trap. I use SnmpSetTranslateMode(SNMPAPI_UNTRANSLATED_V1) in order to do that. I also added the sysUpTime oid (1.3.6.1.2.1.1.3.0), the snmpTrapOID (1.3.6.1.6.3.1.1.4.1.0) in the beginning of the bindings list and the enterpriseOID (1.3.6.1.6.3.1.1.4.3.0) at the end of the bindings list to make it possible to send v1 traps.

Everything is working fine except two (possibly related) things.

The agent-addr field in the trap is always to 0.0.0.0 (I tried adding a snmpTrapAddress oid(1.3.6.1.6.3.18.1.3.0) to the bindings list but that didn’t work). I would like this field to contain the Ip-address of the source.

The second problem is that although I specify an IP-address and a port in a HSNMP_ENTITY with SnmpStrToEntity and SnmpSetPort and I use this HSNMP_ENTITY in the SnmpSendMsg function the trap still gets send from another port (somewhere in the dynamic ports range).

Is there anybody here who has an idea of how to fix this or who can tell me if this is at all possible?

Answer 1

A couple of ideas:

• The agent-addr may be set to the IP address of the network adapter by a lower layer. Is there an option to associate one particular adapter with SNMP?

• Why do you need to set the source port for the trap? SNMP only requires that the trap be sent to UDP port 162; the source is irrelevant unless your specific application has additional requirements. (See RFC 1067 for SNMP details.)