Das Werkstatt

[PROBLEM]
executing some command like this (which should work according to man-pages) gives the error "target problem":

iptables -t nat -I OUTPUT 2 -p tcp --sport 1234 -j DNAT --to 127.0.0.1

or "invalid argument" when using "iptables -t nat -A OUTPUT...".



[SOLUTION]
check if you have activated "CONFIG_IP_NF_NAT_LOCAL" in your kernel settings.

You can also get these very descriptive "target problem" errors if you confuse POSTROUTING with PREROUTING in the nat table when you're trying to setup NAT rules (e.g. adding a rule to POSTROUTING when you want to do DNAT or adding a rule to PREROUTING for SNAT respectively)