diff --git a/gns3server/compute/builtin/nodes/nat.py b/gns3server/compute/builtin/nodes/nat.py
index b2c053f8..ba1b27b5 100644
--- a/gns3server/compute/builtin/nodes/nat.py
+++ b/gns3server/compute/builtin/nodes/nat.py
@@ -42,7 +42,7 @@ class Nat(Cloud):
                 "name": "nat0",
                 "type": "ethernet",
                 "interface": "eth1",
-                "port_number": 1
+                "port_number": 0
             }
         ]
 
diff --git a/gns3server/schemas/port.py b/gns3server/schemas/port.py
index 0e89d665..26c00913 100644
--- a/gns3server/schemas/port.py
+++ b/gns3server/schemas/port.py
@@ -32,7 +32,7 @@ PORT_OBJECT_SCHEMA = {
                 "port_number": {
                     "description": "Port number",
                     "type": "integer",
-                    "minimum": 1
+                    "minimum": 0
                 },
                 "type": {
                     "description": "Port type",
@@ -58,7 +58,7 @@ PORT_OBJECT_SCHEMA = {
                 "port_number": {
                     "description": "Port number",
                     "type": "integer",
-                    "minimum": 1
+                    "minimum": 0
                 },
                 "type": {
                     "description": "Port type",
@@ -84,7 +84,7 @@ PORT_OBJECT_SCHEMA = {
                 "port_number": {
                     "description": "Port number",
                     "type": "integer",
-                    "minimum": 1
+                    "minimum": 0
                 },
                 "type": {
                     "description": "Port type",
diff --git a/tests/compute/builtin/nodes/test_nat.py b/tests/compute/builtin/nodes/test_nat.py
index 88035d97..bd1a6132 100644
--- a/tests/compute/builtin/nodes/test_nat.py
+++ b/tests/compute/builtin/nodes/test_nat.py
@@ -33,7 +33,7 @@ def test_json(on_gns3vm, project):
             {
                 "interface": "eth1",
                 "name": "nat0",
-                "port_number": 1,
+                "port_number": 0,
                 "type": "ethernet"
             }
         ]