OSEC

Neohapsis is currently accepting applications for employment. For more information, please visit our website www.neohapsis.com or email hr@neohapsis.com
 
Subject: Re: bind to specific interface...
From: Jürgen Fluk (louisntm-gmbh.de)
Date: Tue Feb 15 2000 - 01:30:00 CST

Wietse Venema wrote:
>
> [J_rgen] Fluk:
> > > One Postfix can receive mail for any number of IP addresses.
> > >
> > > > I would like to set
> > > > inet_interfaces = <newIP> <oldIP>
> > > > so it listens to both (does work) and would send out on any (the first)
> > > > of them (does not work as both IPs are only aliases and smtp_connect
> > > > does not bind).
> > >
> > > Why are you concerned about the source IP address used for sending
> > > mail?
> >
> > Because that`s the address/name which shows up in the "Received:" headers
> > and the one
> > which one of the outside server will check for detecting relay access.
> > Currently postfix uses the machine's "native" address (in a 192.168.
> > network) and
> > connections appear coming from my MASQuerading gateway. This is not what I
> > want.
> What TCP/IP stack binds to the wrong interface address when making
> connections over the network?
> Wietse

This is a Linux (RedHat 6.0 with 2.2.12 kernel) machine, and has
        eth0 = internal address (192.168...)
        eth0:0 = old external address
        eth0:1 = new external address
If I configure
        inet_interface = old external address
no problem, postfix will listen on this address, and outgoing connections
will bind to it (so appear with the right sender IP).
If I'm in process to switch IP addresses, I think I have to offer service
on both addresses (as DNS takes time to spread around). So I initially
configured
        inet_interface = <old IP> <new IP>
which makes postfix listen on both IPs (and interfaces), but outgoing
connections are not bound (as smtp_connect.c does not do it), and so they
start via the "normal" interface eth0, which has the internal address only.

louis 

-- 
Jürgen Fluk                                 louisntm-gmbh.de
New Technologies Management GmbH            Tel +49 89 993415-56
Stefan-George-Ring 24, D-81929 München      Fax +49 89 993411-99