diff --git a/misc/config_tools/scenario_config/default_populator.py b/misc/config_tools/scenario_config/default_populator.py
index 560f1a885..bc55b26f1 100755
--- a/misc/config_tools/scenario_config/default_populator.py
+++ b/misc/config_tools/scenario_config/default_populator.py
@@ -7,6 +7,7 @@
 
 import os
 import argparse
+import elementpath
 
 from scenario_transformer import ScenarioTransformer
 
@@ -14,9 +15,32 @@ from pipeline import PipelineObject, PipelineStage, PipelineEngine
 from schema_slicer import SlicingSchemaByVMTypeStage
 
 class DefaultValuePopulator(ScenarioTransformer):
+    def get_default_value(self, xsd_element_node, xml_parent_node):
+        # The attribute @default of the xsd:element node
+        v = xsd_element_node.get("default")
+        if v is not None:
+            return v
+
+        # The acrn:defaults and acrn:unique-among annotations which define a set of default values that shall be unique
+        # among a collection of nodes
+        annot_node = self.get_node(xsd_element_node, "xs:annotation")
+        if annot_node is not None:
+            defaults = annot_node.get("{https://projectacrn.org}defaults")
+            unique_among = annot_node.get("{https://projectacrn.org}unique-among")
+            if defaults is not None and unique_among is not None:
+                try:
+                    default_values = set(eval(defaults))
+                    existing_values = set(elementpath.select(self.xml_etree, unique_among, variables={"parent": xml_parent_node}))
+                    available_defaults = default_values - existing_values
+                    return sorted(list(available_defaults))[0]
+                except:
+                    pass
+
+        return None
+
     def add_missing_nodes(self, xsd_element_node, xml_parent_node, new_node_index):
         element_name = xsd_element_node.get("name")
-        default_value = xsd_element_node.get("default")
+        default_value = self.get_default_value(xsd_element_node, xml_parent_node)
 
         # If the node is neither of a complex type (i.e. it does not have an child node) nor has a default value, do not
         # create the node at all. Users are required to fill in proper values in such nodes, and missing any of them
diff --git a/misc/config_tools/scenario_config/scenario_transformer.py b/misc/config_tools/scenario_config/scenario_transformer.py
index 608dff2f6..cec23de2c 100644
--- a/misc/config_tools/scenario_config/scenario_transformer.py
+++ b/misc/config_tools/scenario_config/scenario_transformer.py
@@ -18,6 +18,7 @@ class ScenarioTransformer:
 
     def __init__(self, xsd_etree, visit_optional_node=False):
         self.xsd_etree = xsd_etree
+        self.xml_etree = None
 
         self._visit_optional_node = visit_optional_node
 
@@ -92,7 +93,11 @@ class ScenarioTransformer:
         return []
 
     def transform(self, xml_etree):
+        self.xml_etree = xml_etree
+
         xml_root_node = xml_etree.getroot()
         xsd_root_node = self.get_node(self.xsd_etree, f".//xs:element[@name='{xml_root_node.tag}']")
         if xsd_root_node is not None:
             self.transform_node(xsd_root_node, xml_root_node)
+
+        self.xml_etree = None
diff --git a/misc/config_tools/schema/VMtypes.xsd b/misc/config_tools/schema/VMtypes.xsd
index bd803bd2b..8c2ec68e9 100644
--- a/misc/config_tools/schema/VMtypes.xsd
+++ b/misc/config_tools/schema/VMtypes.xsd
@@ -203,8 +203,8 @@ CLOSID 0 and the second is mapped to virtual CLOSID 1, etc.</xs:documentation>
         <xs:documentation>Specify the COM base for each legacy virtual UART.</xs:documentation>
       </xs:annotation>
     </xs:element>
-    <xs:element name="vbdf" type="VBDFType" minOccurs="0" maxOccurs="1">
-      <xs:annotation acrn:title="Virtual BDF">
+    <xs:element name="vbdf" type="VBDFType">
+      <xs:annotation acrn:title="Virtual BDF" acrn:defaults="[f'00:{i:02x}.0' for i in range(16, 24)]" acrn:unique-among="//vuart_connection/endpoint[vm_name=$parent/vm_name]/vbdf/text()">
         <xs:documentation>Specify the virtual Bus:Device.Function (BDF) for each PCI virtual UART. Virtual BDF is automatically assigned when the configuration is saved and can be changed if needed.</xs:documentation>
       </xs:annotation>
     </xs:element>
diff --git a/misc/config_tools/schema/checks/vbdf_assignment.xsd b/misc/config_tools/schema/checks/vbdf_assignment.xsd
new file mode 100644
index 000000000..5f850872a
--- /dev/null
+++ b/misc/config_tools/schema/checks/vbdf_assignment.xsd
@@ -0,0 +1,17 @@
+<?xml version="1.0"?>
+<!-- Copyright (C) 2022 Intel Corporation. -->
+<!-- SPDX-License-Identifier: BSD-3-Clause -->
+<xs:schema xml:id="root"
+           xmlns:xs="http://www.w3.org/2001/XMLSchema"
+           xmlns:acrn="https://projectacrn.org">
+
+  <xs:assert test="every $root in /acrn-config satisfies
+                   every $vm in $root/vm satisfies
+		   every $vbdf in distinct-values($root/hv//vuart_connection[type='pci']/endpoint[vm_name=$vm/name]/vbdf/text() | $root/hv//IVSHMEM_VM[VM_NAME=$vm/name]/VBDF/text()) satisfies
+		   count($root/hv//vuart_connection[type='pci']/endpoint[vm_name=$vm/name and vbdf=$vbdf] | $root/hv//IVSHMEM_VM[VM_NAME=$vm/name and VBDF=$vbdf]) = 1">
+    <xs:annotation acrn:severity="error" acrn:report-on="$root/hv//vuart_connection[type='pci']/endpoint[vm_name=$vm/name and vbdf=$vbdf] | $root/hv//IVSHMEM_VM[VM_NAME=$vm/name and VBDF=$vbdf]">
+      <xs:documentation>VM "{$vm/name}" contains multiple virtual UART controllers and/or IVSHMEM interfaces using BDF {$vbdf}. Adjust the BDF of those devices.</xs:documentation>
+    </xs:annotation>
+  </xs:assert>
+
+</xs:schema>
diff --git a/misc/config_tools/schema/types.xsd b/misc/config_tools/schema/types.xsd
index 2a47703e1..2dc286574 100644
--- a/misc/config_tools/schema/types.xsd
+++ b/misc/config_tools/schema/types.xsd
@@ -219,7 +219,7 @@ Read more about the available scheduling options in :ref:`cpu_sharing`.</xs:docu
      </xs:annotation>
    </xs:element>
    <xs:element name="VBDF" type = "VBDFType">
-     <xs:annotation acrn:title="Virtual BDF">
+     <xs:annotation acrn:title="Virtual BDF" acrn:defaults="[f'00:{i:02x}.0' for i in range(8, 16)]" acrn:unique-among="//IVSHMEM_VM[VM_NAME=$parent/VM_NAME]/VBDF/text()">
        <xs:documentation>Virtual BDF (Bus Device Function) is automatically assigned and can be changed if needed. Set in Hex.</xs:documentation>
      </xs:annotation>
    </xs:element>