Date: Thu, 04 Mar 2004 11:58:26 +0100 From: Sasa Stupar <sasa@stupar.homelinux.net> To: FreeBSD-config ML <freebsd-config@freebsd.org> Subject: Re: NAT onto same network? Message-ID: <40470BD2.9000001@stupar.homelinux.net> In-Reply-To: <49386.141.67.67.161.1078396444.squirrel@Matrix.Iceman> References: <4046FDDA.7080908@stupar.homelinux.net> <49386.141.67.67.161.1078396444.squirrel@Matrix.Iceman>
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OK, webservers ip is 192.168.10.10, internal IP on nat machine is
192,168.10.111, all users have ip in the range 192.168.10.0/24 mask
255.255.255.0. They are all connected to the switch.
Here is what is says about it but for iptables on linux:
--------
10. Destination NAT Onto the Same Network
If you are doing port forwarding back onto the same network, you need to
make sure that both future packets and reply packets pass through the
NAT box (so they can be altered). The NAT code will now (since
2.4.0-test6), block the outgoing ICMP redirect which is produced when
the NAT'ed packet heads out the same interface it came in on, but the
receiving server will still try to reply directly to the client (which
won't recognize the reply).
The classic case is that internal staff try to access your `public' web
server, which is actually DNAT'ed from the public address (1.2.3.4) to
an internal machine (192.168.1.1), like so:
# iptables -t nat -A PREROUTING -d 1.2.3.4 \
-p tcp --dport 80 -j DNAT --to 192.168.1.1
One way is to run an internal DNS server which knows the real (internal)
IP address of your public web site, and forward all other requests to an
external DNS server. This means that the logging on your web server will
show the internal IP addresses correctly.
The other way is to have the NAT box also map the source IP address to
its own for these connections, fooling the server into replying through
it. In this example, we would do the following (assuming the internal IP
address of the NAT box is 192.168.1.250):
# iptables -t nat -A POSTROUTING -d 192.168.1.1 -s 192.168.1.0/24 \
-p tcp --dport 80 -j SNAT --to 192.168.1.250
Because the PREROUTING rule gets run first, the packets will already be
destined for the internal web server: we can tell which ones are
internally sourced by the source IP addresses.
----------------
Thank you,
Sasa
Frank Mueller pravi:
> Maybe you should give a little more information, what exactly you're trying to do.
> Subnets? Netmasks? Webserver physically only connected to Gateway???
>
> Bye,
>
> Frank
>
>
>>Hi!
>>
>>I have manage to configure NAT, port forwarding and firewall on my new
>>gateway machine. Now I am stuck with configuring nat onto same network.
>>I need it so LAN users can access webserver which is also on the LAN (it
>>has configured multiple virtual hosts).
>>Can anyone help me with this?
>>
>>Thank you,
>>Sasa
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