Redirecting internal tcp connections

Hi, I have a lpd server on a remote host that ISP blocks port 515. I try to use something like "lpr [email protected]:900" but lprng doenst seems to recognize the port argument. So, I think to use iptables to redirect TCP requests on port 515 to port 900 but I dont know how. I've tried the following:

#iptables -A OUTPUT -p tcp --dport 515 -j REDIRECT --to-port 900

This gives me a "iptables: Invalid argument"

Any ideas?

You have to do this in the nat table and the prerouting or output chain, and you should use DNAT instead of REDIRECT, because REDIRECT is for packets with destination your own machine. So we have:

iptables -t nat -A PREROUTING -p tcp --dport 515 -j DNAT --to- destination remotehost.com:900

Regards.

Jose Maria Lopez Hernandez
Director Tecnico de bgSEC
[email protected]
bgSEC Seguridad y Consultoria de Sistemas Informaticos
http://www.bgsec.com
ESPAÑA

The only people for me are the mad ones -- the ones who are mad to live,
mad to talk, mad to be saved, desirous of everything at the same time,
the ones who never yawn or say a commonplace thing, but burn, burn, burn
like fabulous yellow Roman candles.
                -- Jack Kerouac, "On the Road"

I would suggest that you add a destination match as well so that you don't blindly redirect traffic destend to any system's LPD port. I.e. make your IPTables like look like this:

iptables -t nat -A PREROUTING -p tcp -d remotehost.com --dport 515 -j DNAT --to-destination remotehost.com:900

Grant. . . .