Ok, after trying multiple different configurations I decided to play by 
the book - I removed ifcfg script for creating the additional bridge and
 set up an Xen script. So my new configuration is:<br><br>-&gt; eth3 (my physical interface)<br># NetXen Incorporated NX3031 Multifunction 1/10-Gigabit Server Adapter<br>DEVICE=eth3<br>BOOTPROTO=static<br>HWADDR= ...<br>
ONBOOT=yes<br>IPADDR= ...<br>NETMASK= ...<br>NETWORK= ...<br><br>and the network-xen-multi-bridge script:<br><br>#!/bin/sh<br># network-xen-multi-bridge<br># Exit if anything goes wrong.<br>set -e<br># First arg is the operation.<br>
OP=$1<br>shift<br>script=/etc/xen/scripts/network-bridge.xen<br>case ${OP} in<br>start)<br>        $script start vifnum=3 bridge=xenbr3 netdev=eth3<br>        $script start vifnum=0 bridge=xenbr0 netdev=eth0<br>        ;;<br>
stop)<br>        $script stop vifnum=3 bridge=xenbr3 netdev=eth3<br>        $script stop vifnum=0 bridge=xenbr0 netdev=eth0<br>        ;;<br>status)<br>        $script status vifnum=3 bridge=xenbr3 netdev=eth3<br>        $script status vifnum=0 bridge=xenbr0 netdev=eth0<br>
        ;;<br>*)<br>        echo &#39;Unknown command: &#39; ${OP}<br>        echo &#39;Valid commands are: start, stop, status&#39;<br>        exit 1<br>esac<br><br>After I restart the physical server bridges are set up correctly:<br>
<br># brctl show<br>bridge name     bridge id               STP enabled     interfaces<br>virbr0          8000.000000000000       yes<br>xenbr0          8000.feffffffffff       no              vif0.0<br>                                                                  peth0<br>
xenbr3          8000.feffffffffff       no              vif0.3<br>                                                                 peth3<br><br>Unfortunately,
 this did not solve the problem - I manage to start one VM (connected to
 both of the bridges), but when I try to start the other one, it just 
hangs when trying to bring up the second interface (connected to xenbr3)
 :/<br><br>I&#39;m currently completely out of ideas, but I&#39;m not giving up ;)