Hello everybody!

I've got a situation where I need to setup something that does the following:

Host: 1.2.3.4 Port 1234

Remote Host 5.6.7.8 Port 5678

If I connect to host 1.2.3.4:1234 it forwards things to 5.6.7.8:5678

1.2.3.4:1234 should accept any connection on there and just foward it on...

I've seen some examples with IPTables doing this...these seem to be for the
software/connections that originate on that host to be forwarded, but not
something that comes in via net, ie:

9.0.1.2.3:1234 - > 1.2.3.4:1234 - > 5.6.7.8:5678

Basically this is just "proxy" in other words to the host...but this would be
TCP or UDP traffic that comes in...

A VPN via say OpenVPN to this host and forward everything out is one solution,
but for this case its not an option... I really only need to forward ONE
SPECIFIC HOST:PORT to ONE SPECIFIC REMOTE HOST:PORT. I don't want to forward
out all traffic via the VPN to this host, and then on... I've got other things
that are VPN'd out to places...

I really just want to be able to point the software that I need to do this at
this 1.2.3.4:5678 and it forwards everything to 5.6.7.8:5678 TCP/UDP

I am NOT an iptables guru.... I probably could do this with some Cisco IOS
stuff if I had it at the location, but this is not a colo right now...

Any one have other suggestions or solutions???



An example of what I've seen in various similar forms on various sites:

https://www.debuntu.org/how-to-redirecting-network-traffic-to-a-new-ip-using-ip
tables/


# echo "1" > /proc/sys/net/ipv4/ip_forward

or

# sysctl net.ipv4.ip_forward=1

Then, we will add a rule telling to forward the traffic on port 1111 to ip
2.2.2.2 on port 1111:

# iptables -t nat -A PREROUTING -p tcp --dport 1111 -j DNAT --to-destination
2.2.2.2:1111

and finally, we ask IPtables to masquerade:

iptables -t nat -A POSTROUTING -j MASQUERADE

Optionally, you could only redirect the traffic from a specific source/network
with, for a host only:

# iptables -t nat -A PREROUTING -s 192.168.1.1 -p tcp --dport 1111 -j DNAT
--to-destination 2.2.2.2:1111

or for a whole network

# iptables -t nat -A PREROUTING -s 192.168.1.0/24 -p tcp --dport 1111 -j DNAT
--to-destination 2.2.2.2:1111





Rick


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