Home / server / Questions / 406679
Accepted
Mahendra Liya
Asked: 2012-07-12 01:17:31 +0800 CST

How to route UDP traffic from one public IP (linux) to another public IP(Windows)

  • 772

I want to prevent direct access of my Windows Machine and want to expose some programs running on it via my Linux Machine (which again is accessible by a Public IP).

Is there a way where-in I can configure my Linux Machine (say IP = a.b.c.d) to route all the UDP traffic which it gets at a specific port (say 6667) to my Windows Machine (say IP = e.f.g.h) at port 6668?

Is yes, how can I implement it?

UPDATE

# bindadress    bindport  connectaddress  connectport

192.168.2.45    6667    192.168.2.104   6668

# logging information
logfile /var/log/rinetd.log

# uncomment the following line if you want web-server style logfile format
logcommon
~

UPDATE

I wish to route UDP traffic only.

ip forwarding route linux-networking

2 Answers

  1. Best Answer

    The following section works for TCP only (This was published before Mahendra changed the title

    Install rinetd. In this program you can configure incoming port and outgoing port easily. First install the program. Then change /etc/rinetd.conf

    Ex:

    #bindadress bindport connectaddress connectport

    a.b.c.d 6667 e.f.g.h 6668

    For UDP check the link below

    http://brokestream.com/udp_redirect.html

    This is from the chat discussion which actually solved the problem

    iptables -t nat -A PREROUTING -i $EXT_IF -p udp -d $EXT_IP --dport 53 -j DNAT --to-destination $INTERNAL_SERVER

and make sure you also have it allowed to pass through the FORWARD chain with something like

#forward traffic
iptables -A FORWARD -i $EXT_IF -o $INT_IF -p udp -d $INTERNAL_SERVER --dport 53 -j ACCEPT
#reply traffic
iptables -A INPUT -o $EXT_IF -i $INT_IF -p udp -s $INTERNAL_SERVER --sport 53 -m state --state ESTABLISHED,RELATED -j ACCEPT
    • 4

  2. Yes, this is called reverse NAT and is part of the IpTables capabilities of Linux. Every decent NATtins firewall does that to expose services.

    • 1