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Re: [suse-security] another 3-interface firewall problem (two external, no DMZ)



You could check the following:
1) Is the routing ok ?
2) Are there any firewall log entries ?
3) Are you sure you don't masq your webserver's reply packets with the wrong IP ? (I understand that you now have 2 external IPs)

You could get more info by tcpdumping your interfaces.

Andreas


On Sunday 04 January 2004 00:00, Dr. Peter Münstermann wrote:
> Hi,
>
> I am running a small enterprise server under Suse 9.0.
> The main tasks are: Masquerading an internal network, SMTP, POP3 and web
> serving.
>
> Everything works nice with two interfaces:
> eth0: 1.2.3.4 netmask 255.255.255.192 (leased line with static IP)
> eth1: 192.168.0.1 netmask 255.255.255.0 (internal network)
> with default route 1.2.3.3
> Web server is listening on 1.2.3.4, SMTP on both interfaces, POP3 only at
> the internal interface
>
> NOW: to keep traffic costs as low as possible, we like to route the main
> traffic over a DSL flat rate.
> Configuring the DSL stuff gives the aditional ppp0 interface (PPPoE with
> eth2), masquerading works and I can see the web server at 1.2.3.4 due to
> the additional entry:
> iptables -A INPUT -i eth1 -s 192.168.0.0/24 -d 1.2.3.4 -j ACCEPT
>
> BUT: The address 1.2.3.4 is not responding from the outside any more.
> Both eth0 and ppp0 are configured as external interfaces in the
> SuSEfirewall configuration.
>
> I think, the problem can be seen as a sort of load balancing for the
> leaving IP packets.
>
> Any hints, how to get the official external IP address working again ?
>
>
> Best regards
>     Peter


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