KVM network configuration issue

[jurgen.depicker at let.be]

Hi all.
I have a KVM guest webserver VWEB which I want to give an external IP.  My 
host has 4 NICs, of which I use only one presently. 

Host:
auto eth0
iface eth0 inet manual
auto br0
iface br0 inet static
address 172.16.5.11
netmask 255.255.0.0
gateway 172.16.1.1
dns-nameservers 172.16.1.2
bridge-ports eth0

I would like to connect a cable between my host's eth3 and my company FW. 
(That specific port of the FW is now in use by my old physical web server 
and all is working fine for this old server).
VWEB should use eth3 on the host.  And inside VWEB, i want to assign the 
fixed external IP.

I cannot find the doc for this setup.  I tried the following:
Host: i added the following:
auto br1
iface br1 inet manual
bridge-ports eth3

-> i didn't want my host to have this external ip available, only VWEB 
running as guest, so on the host I didn't configure the external IP.  I 
expected the packets form VWEB to be just passed to the interface.  It 
didn't work.  I have some ideas about why it may not work, but I can't 
solve it.  Anyone knows how to do this?

Kind regards, 

Jürgen
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