ip tables port fwd duplicates packets

Question

i want to fwd the udp packets that are received on port 162 to another port.ex:8981

i have executed the following cmd

iptables -A PREROUTING -t nat  -p tcp --dport 162 -j REDIRECT --to-port 8981

I see that i am recieving duplicates packets now on 8981..

could some one guide me the right way of doing it?

Also how to delete the above rule ?

TIA, /d

your question says udp and your `code snippet` says tcp. which is it? — jamesbtate, Aug 06 '11 at 11:30

womble · Accepted Answer · 2011-08-07T17:46:51.620

We'll leave the "duplicate packets" problem until there's some more diagnostic data available, but the rule deletion is easy.

To delete an iptables rule, simply replace the -A with -D:

iptables -D PREROUTING -t nat  -p tcp --dport 162 -j REDIRECT --to-port 8981

If you're using -I N instead, you can use iptables -D N, but that's risky if there have been any rules inserted subsequently.

If you've really screwed up and don't even know what iptables command you ran (bash has command history for a reason...) then you can list all the rules in a chain like this:

iptables -t nat -L PREROUTING --line-numbers

Which will get you output like this:

Chain int2ext (1 references)
num  target     prot opt source               destination
1    ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           ctstate RELATED,ESTABLISHED
2    ACCEPT     all  --  192.0.2.0/24         0.0.0.0/0
3    ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0           udp dpt:53
4    ACCEPT     icmp --  0.0.0.0/0            0.0.0.0/0

Then, find the num column entry corresponding to the rule you want to delete, and run

iptables -t nat -D PREROUTING <num>

hi thanks for the reply, now as pudding fox points out , i may have used tcp there in cmd..also iam not quite sure of the cmd use..is there a way to see my rule using iptables and delete it? — Inv3r53, Aug 07 '11 at 11:05
i only want to redirect packets on same host from port 162 to another one as i cannot open socket on port < 1024 , due to permissions problem. — Inv3r53, Aug 07 '11 at 11:07

ip tables port fwd duplicates packets

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