The REDIRECT target is used to redirect packets and streams to the machine itself. This means that we could for example REDIRECT all packets destined for the HTTP ports to an HTTP proxy like squid, on our own host. Locally generated packets are mapped to the 127.0.0.1 address. In other words, this rewrites the destination address to our own host for packets that are forwarded, or something alike. The REDIRECT target is extremely good to use when we want, for example, transparent proxying, where the LAN hosts do not know about the proxy at all.
Note that the REDIRECT target is only valid within the PREROUTING and OUTPUT chains of the nat table. It is also valid within user-defined chains that are only called from those chains, and nowhere else. The REDIRECT target takes only one option, as described below.
Table 11-13. REDIRECT target options
|iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-ports 8080
The --to-ports option specifies the destination port, or port range, to use. Without the --to-ports option, the destination port is never altered. This is specified, as above, --to-ports 8080 in case we only want to specify one port. If we would want to specify a port range, we would do it like --to-ports 8080-8090, which tells the REDIRECT target to redirect the packets to the ports 8080 through 8090. Note that this option is only available in rules specifying the TCP or UDP protocol with the --protocol matcher, since it wouldn't make any sense anywhere else.
Works under Linux kernel 2.3, 2.4, 2.5 and 2.6.