strange udp redirect problem

[Brane F. Gračnar]

Hello there.

I have strange udp port redirection problem.


Here is my setup:


A (192.168.221.101) -> (192.168.221.100) GW (192.168.222.100) ->
(192.168.222.101) B

I would like to redirect packet when A would sends udp packet to
192.168.222.101 port 6000 to 192.168.221.100 port 7000 where runs udp
proxy server.

Well, hosts A and B can ping/telnet eachother, but port redirect does not
work:

iptables -t nat -A PREROUTING -p udp --dport 6000 -j REDIRECT --to-port 7000

Well, noting happens... packets traverse firewall/gw without any
redirection...

Why?

The same thing works flawlessly with tcp protocol (-p tcp, running tcp
listening server on port 7000)...

What am i doing wrong?

Brane