is there any way to duplicate incoming udp traffic on port 162 and forward to multi ports like 162 itself and 1600? I was checking iptables but it seems only able to redirect to a single port/host.
There is an experimental TEE target to iptables' mangle table which is part of the Xtables-addons (ex patch-o-matic) which is able to copy a packet without changes to another gateway. There you could NAT to another port, if still needed.
flow-fanout will do what you want:
I'm pretty sure you can also configure net-snmp as a trap receiver to relay traps to other devices if you have multiple monitoring stations you are trying to send data to.
I just found samplicator which also seems to do this.