How to duplicate packets?

Hi is there a way to duplicate every arrived and send packet from specific device in my LAN ??

By ip tables maybe or something else?

Matter of fact you can what you're trying to do is named port/traffic mirroring, usually done for monitoring purposes. Iptables offers you different angles to tackle the subject.

I mean etc...from internet to my lan ( arrived a udp packet at port 3074...i want to duplicate it...the same from to internet... one packet generated from but in internet goes two (duplicate).

How can i do this?

Look a netem:

Why do you want to duplicate the packets?

For test something in online gaming....i dont know which command to use for netem.

I would call this an advanced networking project. you would need to set up several queues and then filter the game traffic into a queue that has netem installed. also it will not work with SQM, so you would have to customize things entirely if you want any kind of bufferbloat protection.

if you can't read the tc-netem man page and figure out what to do, I don't think this project is a good one for you.