diff --git a/.unreleased/fix_port_parity b/.unreleased/fix_port_parity
new file mode 100644
index 000000000..e69de29bb
diff --git a/nat-lab/tests/conftest.py b/nat-lab/tests/conftest.py
index 2d7028875..4a534a52f 100644
--- a/nat-lab/tests/conftest.py
+++ b/nat-lab/tests/conftest.py
@@ -74,6 +74,10 @@ async def on_output(output: str) -> None:
 
     start_port = random.randint(5000, 55000)
     num_ports = random.randint(2000, 5000)
+
+    if start_port % 2 == num_ports % 2:
+        start_port += 1
+
     print(
         datetime.now(),
         f"Setting up ports for {vm_tag}: start={start_port}, num={num_ports}",