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I have a server with a LAN facing address of (eth0) and another LAN facing address of (eth1).

On this server I have a Virtualbox instance of fedora running an apache webserver (on port 8080) with a bridged interface to eth1 on the host server with address of

Users on the 192.168.6.x network can access the Webserver on the Vbox instance ( with no problems.

My question is what kind of iptables entries or commands should be made/executed so as to allow for users on the 192.168.5.x network to access the webserver on the vbox instance. (I'm hoping their url can be something like:

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3 Answers 3

There are only a few options in this instance: 1) Allow direct routing of hosts on the 192.168.5.x network to the 192.168.6.x network. (i.e a route to your network through your intermediate host and ip forwarding enabled in the kernel.

2) Port forward 8080 to the correct ip and port (check out balance-ng and run it on the eth0 interface)

3) iptables based port forwarding / nat

/sbin/iptables -t nat -A PREROUTING -p tcp -i eth0 -d --dport 8080 -j DNAT --to
/sbin/iptables -A FORWARD -p tcp -i eth0 -d --dport 80 -j ACCEPT

enable ip forwarding echo 1 > /proc/sys/net/ipv4/ip_forward

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@Matty: I've tried this, and it doesn't seem to work. Should there be a postrouting rule that handles packets coming from the webserver to the clients on the 192.168.5.x n/w ? – Darider Nov 3 '09 at 23:39
like.... /sbin/iptables -t nat -A POSTROUTING -p tcp -o eth0 -s --to-source I'm not sure that would be necessary. But if you have no other rules, and you aren't using conntrack then it might be. You can also add state tracking. /sbin/iptables -A FORWARD -p tcp -i eth0 -d --dport 80 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT /sbin/iptables -A FORWARD -p tcp -o eth0 -m state --state RELATED,ESTABLISHED -j ACCEPT – MattyB Nov 4 '09 at 0:07
The problem is the packets reaching the web-server have an ip of the 192.168.5.x domain, the webserver doesn't do anything with them doesn't even provide a response. Is there some kind of masquarding rule that can be applied such that the packets get the secondary ip of the main server (eg: – Darider Nov 4 '09 at 2:51
Does the virtual box not have a route to the 192.168.5 network through the intermediate host? It needs a route through the local host operating system since its doing the routing. – MattyB Nov 4 '09 at 4:11
the vbox instance is on the 192.168.6.x n/w is doesn't know about routing to 192.168.5.x n/w i was hoping iptable rules would do all the necessary packet munging. is there something i can do to fix this issue? – Darider Nov 4 '09 at 7:44

For me, the following worked:

sbin/iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
sbin/iptables -t nat -A PREROUTING -p tcp -i eth0  --dport 80 -j DNAT --to

using virtualbox 3.2.12 on ubuntu 10.04 host. What the other answers did not mention is the masquerading, which in my understanding is nessessary to get the answer pakets out correctly.

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This should forward requests on port 8080 on interface eth0 to on interface eth1 on port 8080.

iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 8080 --to-destination -j DNAT
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