diff --git a/confluent_server/confluent/config/configmanager.py b/confluent_server/confluent/config/configmanager.py
index 36187373..a5132e93 100644
--- a/confluent_server/confluent/config/configmanager.py
+++ b/confluent_server/confluent/config/configmanager.py
@@ -1142,7 +1142,10 @@ class _ExpressionFormat(string.Formatter):
                 # such as 'net.pxe.hwaddr'
                 key = '.' + left.attr + key
                 left = left.value
-            key = left.id + key
+            if isinstance(left, ast.Name):
+                key = left.id + key
+            else:
+                raise ValueError("Invalid AST structure: expected ast.Name at end of attribute chain")
             if (not key.startswith('custom.') and
                         _get_valid_attrname(key) not in allattributes.node):
                 raise ValueError(
@@ -1203,6 +1206,34 @@ class _ExpressionFormat(string.Formatter):
                 return strval[index]
         elif isinstance(node, ast.Constant):
             return node.value
+        elif isinstance(node, ast.Call):
+            key = ''
+            if isinstance(node.func, ast.Attribute):
+                fun_name = node.func.attr
+                left = node.func.value
+                while isinstance(left, ast.Attribute):
+                    # Loop through, to handle multi dot expressions
+                    # such as 'net.pxe.hwaddr'
+                    key = '.' + left.attr + key
+                    left = left.value
+                if isinstance(left, ast.Name):
+                    key = left.id + key
+                else:
+                    raise ValueError("Invalid AST structure: expected ast.Name at end of attribute chain")
+            else:
+                raise ValueError(f"Unsupported function in expression")
+            if fun_name == 'replace':
+                if len(node.args) != 2:
+                    raise ValueError("Invalid number of arguments to replace")
+                arg1 = self._handle_ast_node(node.args[0])
+                arg2 = self._handle_ast_node(node.args[1])
+                if key in ('node', 'nodename'):
+                    keyval = self._nodename
+                else:
+                    keyval = self._expand_attribute(key).get('value', '')
+                return keyval.replace(arg1, arg2)
+            else:
+                raise ValueError("Unsupported function in expression")
         else:
             raise ValueError("Unrecognized expression syntax")