Forward udp and tcp to another external IP address.

Gavin Hamill gdh at
Tue Aug 23 13:53:09 CEST 2005

On Monday 22 August 2005 17:09, John Kielkopf wrote:
> We're planning on moving a server to another location and to ease to
> move we'd like to for forward all TCP and UDP traffic coming in on a
> particular IP address at location A to a different address at location
> B.  Note that these addresses are from two different hosts.

Here's a standard recipe I've used for doing this..

# Make the firewall act as a non-caching TCP proxy. Useful for machine moves 
whilst DNS propogates.

$IPTABLES -t nat -A PREROUTING -p tcp --dport 80 -d -j DNAT 
$IPTABLES -A FORWARD -p tcp --dport 80 -d -j ACCEPT
$IPTABLES -t nat -A POSTROUTING -p tcp --dport 80 -d -j SNAT --to

In this case, a web server was runnning on that we were 
physically moving to a new location at

These rules were loaded onto the firewall at


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