Subject: Re: IP Forwarding works only when tcpdump'ing (1.4.2)
To: Frederik Meerwaldt <Meerwaldt@t-online.de>
From: Andrew Brown <atatat@atatdot.net>
List: port-i386
Date: 05/22/2000 14:52:57
>Enabling the promiscious mode should do the trick. I'm only working with
>FreeBSD on PCs, but there it's done with ifconfig <interface> promisc
actually...this can have "undesirable" side-effects. i had a machine
once where if the card was in promiscuous mode and it was forwarding,
it would also forward local datagrams. the most colourful
demonstration of this would be with these three machines:
r (the router) at 192.168.0.1
a (a host) at 192.168.0.2
b (another host) at 192.168.0.3
if a pings b, r (in promiscuous mode) would receive the packet and
forward it. b would then receive two echo requests, and respond to
them both. r would then see two echo replies and forward them as
well. a ends up getting four times the number of replies one would
sanely expect.
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