Virtual Firewall

Hello,

have been trying to build a virtual firewall as a POC but having some difficulty with the networking aspect. On the physical server I have a single NIC that is connected to the Internet with the IP XXX.XXX.XXX.10 and is bound to bridge0. I created the first guest, as the firewall, and added a virtio interface with source type "Host device vnet (bridge0)". At the guest OS level I assigned the NIC another public IP XXX.XXX.XXX.20 and was able to route quite happily to the Internet. I then proceeded to add a second NIC to the firewall guest but this time using the default NAT network and gave it the address 192.168.1.1. I then created another guest with the IP 192.168.1.2 with its default route being 192.168.1.1 and that could get out to the Internet as-well once the FORWARD+SNAT rules w
ere added to iptables.

Now here in lies the problem. I wish to add another network so that I end up with:

XXX.XXX.XXX.20 Public Facing
192.168.1.1 Private LAN
192.168.2.1 DMZ

So using virtual-manager I created two brand new networks called "PrivateLAN" and "DMZ" with the networks above. I then removed the secondary interface from the firewall and added two new NICs, one being on the PrivateLAN and the other on the DMZ. When I fired up the firewall and attempted to assign those IP addresses to the interfaces the response was:

[root@fw1 ~]# ifup eth1
Error, some other host already uses address 192.168.1.1.

[root@fw1 ~]# ifup eth2
Error, some other host already uses address 192.168.2.1.

Running an arping showed that the MAC for bridge0 already had those IPs registered ?!?!? I am obviously missing a networking fundamental here and really would like some help.

If you have only one physical NIC how do you create multiple networks as above; that allows IPtables to control the traffic flow.

Any help gratefully appreciated.

Thanks.

----- Original Message -----

This is well supported in libvirt [1]
If you don't want to use libvirt then you can at least run to test the rules that are created or look at the code.

[1] http://libvirt.org/firewall.html

----- Original Message -----
From: "Andrew Cathrow" <[email protected]>
To: "Phil Daws" <[email protected]>
Cc: [email protected]
Sent: Thursday, 14 March, 2013 3:30:50 PM
Subject: Re: Virtual Firewall

----- Original Message -----

This is well supported in libvirt [1]
If you don't want to use libvirt then you can at least run to test the rules that are created or look at the code.

[1] http://libvirt.org/firewall.html

Thank you Andrew. I believe the underlying problem is my understanding of how KVM handles network interfaces. You have bridge, macvtap, nat etc. All I wish todo is to have one physical bridged network and X+ virtual networks that can route through a single guest. Is that impossible ? I don't think it is as I can do two networks with the default NAT.

Thanks.