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Subject: Re: bind to specific interface...
From: Wietse Venema (wietseporcupine.org)
Date: Tue Feb 15 2000 - 07:52:04 CST

So assign the new IP address to the ethernet interface, and
make the old IP address an alias. End of problem.

        Wietse

[J_rgen] Fluk:
> 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
> --
> J_rgen Fluk louisntm-gmbh.de
> New Technologies Management GmbH Tel +49 89 993415-56
> Stefan-George-Ring 24, D-81929 M_nchen Fax +49 89 993411-99
>
>
>