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Date:      Thu, 27 Jul 2000 01:35:32 +0200 (MEST)
From:      Sven Anderson <sanders@maelstrom.anderson.de>
To:        Nick Rogness <nick@rapidnet.com>, freebsd-net@freebsd.org
Subject:   Re: no static NAT for router itself?
Message-ID:  <Pine.LNX.4.21.0007270121420.16222-100000@maelstrom.anderson.de>
In-Reply-To: <Pine.BSF.4.21.0007261204140.48391-100000@rapidnet.com>

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On Wed, 26 Jul 2000, Nick Rogness wrote:

> > stoffel:~ # ifconfig -a
> > ed1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
> >         inet 134.76.25.223 netmask 0xffffff00 broadcast 134.76.25.255
> >         inet 134.76.25.224 netmask 0xffffffff broadcast 134.76.25.224
> >         inet 134.76.25.225 netmask 0xffffffff broadcast 134.76.25.225
> 
> 
> 	Why do you have these addresses bound to this card?  Is
> 	your provider routing them to you?

There's no provider, it's a subnet of the university-network. Our three
IPs aren't directly routed to us, so i have to "catch it" by Proxy-ARP.

> > What does not work:
> > 
> > Packets originating from the router to one of the external aliased IPs,
> > f.e. 134.76.25.224, are nated correctly to the internal IP 172.27.7.23,
> > BUT the source address of the packet is not 134.76.25.223 (the router) as
> > it should be but 134.76.25.224 (the NAT-alias)! If i look at the netmask
> > of the alias-interface this is actually correct, because the netmask fits
> > exactly 134.76.25.224, so that the source-address is set to the IP of
> > the interface, which is the same IP. To prevent this, a netmask that
> > matches never is needed.
> 
> 	Have you tried the -alias_address option instead of -n ?

The alias_address is for the masquerading (many host share one real IP),
which works fine. The problem appears only with the static 1:1 NAT IPs.

> > Well, so I assumed, that defining the external IPs as alias-interfaces is
> > not the right way to do static NAT (btw.: why there is no HOWTO for this,
> > is static NAT really used so seldom?). So I tried catching the external
> 
> 	No, I use it all of the time as (I assume) many people do.

So please tell me, can you connect _from_ the NATing host to an _internal_
host by it's _public_ IP? And if yes, what is you exact setup?

Thanks,

	Sven

- -- 
_mailto:sven@anderson.de _tel:+49-551-9969285 _tel:+49-179-4939223
_http://tuttle.home.pages.de         _irc://IRCNet/tuttle,isnick
    "Macht verrueckt, was Euch verrueckt macht!" (Blumfeld)

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