Index: xen-3.0.3-testing/tools/examples/xend-config.sxp
===================================================================
--- xen-3.0.3-testing.orig/tools/examples/xend-config.sxp
+++ xen-3.0.3-testing/tools/examples/xend-config.sxp
@@ -76,7 +76,8 @@
 #
 # (network-script 'network-bridge netdev=eth1')
 #
-# The bridge is named xenbr0, by default.  To rename the bridge, use
+# The bridge is named to match the outgoing interface, by default.  For example,
+# eth1 is on xenbr1.  To rename the bridge, use
 #
 # (network-script 'network-bridge bridge=<name>')
 #
Index: xen-3.0.3-testing/tools/ioemu/vl.c
===================================================================
--- xen-3.0.3-testing.orig/tools/ioemu/vl.c
+++ xen-3.0.3-testing/tools/ioemu/vl.c
@@ -89,7 +89,6 @@
 #include "exec-all.h"
 
 #define DEFAULT_NETWORK_SCRIPT "/etc/xen/qemu-ifup"
-#define DEFAULT_BRIDGE "xenbr0"
 
 //#define DEBUG_UNUSED_IOPORT
 //#define DEBUG_IOPORT
@@ -3773,10 +3772,10 @@ int net_client_init(const char *str)
             if (get_param_value(setup_script, sizeof(setup_script), "script", p) == 0) {
                 pstrcpy(setup_script, sizeof(setup_script), DEFAULT_NETWORK_SCRIPT);
             }
-            if (get_param_value(bridge, sizeof(bridge), "bridge", p) == 0) {
-                pstrcpy(bridge, sizeof(bridge), DEFAULT_BRIDGE);
-            }
-            ret = net_tap_init(vlan, ifname, setup_script, bridge);
+            if (get_param_value(bridge, sizeof(bridge), "bridge", p) == 0)
+                ret = net_tap_init(vlan, ifname, setup_script, NULL);
+            else
+                ret = net_tap_init(vlan, ifname, setup_script, bridge);
         }
     } else
 #endif
Index: xen-3.0.3-testing/tools/python/xen/xend/image.py
===================================================================
--- xen-3.0.3-testing.orig/tools/python/xen/xend/image.py
+++ xen-3.0.3-testing/tools/python/xen/xend/image.py
@@ -339,13 +339,16 @@ class HVMImageHandler(ImageHandler):
                 mac = sxp.child_value(info, 'mac')
                 if mac == None:
                     mac = randomMAC()
-                bridge = sxp.child_value(info, 'bridge', 'xenbr0')
+                bridge = sxp.child_value(info, 'bridge', None)
                 model = sxp.child_value(info, 'model', 'rtl8139')
                 ret.append("-net")
                 ret.append("nic,vlan=%d,macaddr=%s,model=%s" %
                            (nics, mac, model))
                 ret.append("-net")
-                ret.append("tap,vlan=%d,bridge=%s" % (nics, bridge))
+                net = "tap,vlan=%d" % (nics,)
+                if bridge:
+                    net += ",bridge=%s" % (bridge,)
+                ret.append(net)
         return ret
 
     def configVNC(self, config):
Index: xen-3.0.3-testing/tools/ioemu/target-i386-dm/qemu-ifup
===================================================================
--- xen-3.0.3-testing.orig/tools/ioemu/target-i386-dm/qemu-ifup
+++ xen-3.0.3-testing/tools/ioemu/target-i386-dm/qemu-ifup
@@ -1,10 +1,11 @@
 #!/bin/sh
 
-#. /etc/rc.d/init.d/functions
-#ulimit -c unlimited
-
-echo -c 'config qemu network with xen bridge for '
-echo $*
+bridge=$2
+if [ -z "$bridge" ]; then
+    brnum=$(ip route list | awk '/^default / { print $NF }' | sed 's/^[^0-9]*//')
+    brnum=${brnum:-0}
+    bridge=xenbr${brnum}
+fi
 
 ifconfig $1 0.0.0.0 up
-brctl addif $2 $1
+brctl addif $bridge $1