Hi, For some special reasons I want to alter the IP address of outgoing packets that are generated locally to a secondary IP address on my machine. For a test I use the udp/echo service. Without any rules a tcpdump looks like this: 192.168.56.101 is the primary address of the echo server and 192.168.56.16 is the secondary address of the interface. 08:24:04.063987 IP 192.168.56.1.48462 > 192.168.56.16.echo: UDP, length 6 08:24:04.064522 IP 192.168.56.101.echo > 192.168.56.1.48462: UDP, length 6 So I add the iptables rule: iptables -t nat -I POSTROUTING -p udp -s 192.168.56.101 --sport 7 \ -j SNAT --to-source 192.168.56.16 now tcpdump shows that no answer packet is sent out any more: 08:24:16.851095 IP 192.168.56.1.55362 > 192.168.56.16.echo: UDP, length 6 With iptables -t nat -L POSTROUTING I can see that the rule is hit since the counter increases. Also a iptables TRACE shows me that the rule is hit. No filter appears in the TRACE log. Any ideas where the packet vanished? Mit freundlichen Grüßen, Michael Schwartzkopff -- [*] sys4 AG http://sys4.de, +49 (89) 30 90 46 64, +49 (162) 165 0044 Franziskanerstraße 15, 81669 München Sitz der Gesellschaft: München, Amtsgericht München: HRB 199263 Vorstand: Patrick Ben Koetter, Marc Schiffbauer Aufsichtsratsvorsitzender: Florian Kirstein
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