Virtual Firewall

[Phil Daws <uxbod@splatnix.net>]

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.