From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pascal Hambourg Subject: Re: Ignorance about combining two net connections Date: Sun, 14 Oct 2007 15:57:00 +0200 Message-ID: <4712202C.9060301@plouf.fr.eu.org> References: <20071014123703.GA30106@crowfix.com> Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20071014123703.GA30106@crowfix.com> Sender: netfilter-owner@vger.kernel.org List-Id: Content-Type: text/plain; charset="iso-8859-1"; format="flowed" To: netfilter@vger.kernel.org Hello, felix@crowfix.com a =E9crit : [...] > For instance, I know that when a client connects to a > remote server's port 25, when the server accept()s the connection, it > assigns a new temporary port to that connection. Huh ? What are you talking about ? Aren't you confusing with FTP ? > Suppose I have an iptables rule which sends all outgoing traffic with > a destination port of 25 down the static pipe. You need more thant a simple iptables rule. Iptables will just mark the= =20 packets and do some NAT if required, you need also advanced routing to=20 route marked packets through the proper interface. See the LARTC howto.= =20 Do not forget to disable source address validation (rp_filter). [cut irrelevant stuff] > Incoming to the local SMTP server doesn't need any attention, right? Reply traffic of incoming connections must be routed through the same=20 ISP, because the other ISP may consider it as IP spoofing and drop it.=20 This also requires advanced routing.