snmptrap v2: how to set the agent address?

hello,all

    I wonder how to set the  agent address(not the adress of the machine
the send the trap) in snmptrap for snmp v2?

for the snmptrap command:
snmptrap -v 1 [COMMON OPTIONS] [-Ci] enterprise-oid agent generic-trap specific-trap uptime [OID TYPE VALUE]... 
snmptrap -v [2c|3] [COMMON OPTIONS] [-Ci] uptime trap-oid [OID TYPE VALUE]...

from the command option, for v1, there is a agent to set the agent adress. But for v2,
there is no such agent. I have search long but have no result. It quite confuses me.
any help?

thanks,
PanTao