redirect 127.0.0.1:25 -> 127.0.0.1:2000

Hi folks.

I'm using a nat PREROUTING rule to forward all connections from port 25 to port 2000. This works fine for all addresses except for localhost.

the rule i'm using is: "-A PREROUTING -p tcp -m tcp --dport 25 -j REDIRECT --to-ports 2000" (CentOS4, kernel 2.6.9-55, iptables-1.2.11)

For example, on my machine: foobar.example.com

If i telnet from any machine other than foobar.example.com to foobar.example.com:25, the connection is redirected properly to foobar.example.com:2000. However, if i telnet from foobar.example.com to localhost:25, i get a connection refused.
Telnetting to from foobar.example.com to localhost:2000 works fine (as expected)

Telnetting from foobar.example.com to foobar.example.com:25 also does not work.

I know that you can't do prerouting from localhost -> some.other.host (or vice versa), but i thought localhost->localhost would work.

Am i screwing up the rule? Should I add another rule? Or am i just SOL.

Thanks.

...alex...

Hi folks.

I'm using a nat PREROUTING rule to forward all connections from port 25 to port 2000. This works fine for all addresses except for localhost.

the rule i'm using is: "-A PREROUTING -p tcp -m tcp --dport 25 -j REDIRECT --to-ports 2000" (CentOS4, kernel 2.6.9-55, iptables-1.2.11)

For example, on my machine: foobar.example.com

If i telnet from any machine other than foobar.example.com to foobar.example.com:25, the connection is redirected properly to foobar.example.com:2000. However, if i telnet from foobar.example.com to localhost:25, i get a connection refused.
Telnetting to from foobar.example.com to localhost:2000 works fine (as expected)

Telnetting from foobar.example.com to foobar.example.com:25 also does not work.

I know that you can't do prerouting from localhost -> some.other.host (or vice versa), but i thought localhost->localhost would work.

Am i screwing up the rule? Should I add another rule? Or am i just SOL.

Thanks.

...alex...

which answered my question.
I verified that the kernel had IP_NF_NAT_LOCAL set to y, and i see that I was missing the "iptables -t nat -A OUTUPT" line. Everything works now. Whoohoo!