diff --git a/core/device/fd/fd.go b/core/device/fd/fd.go
index 95e6257..0e5c66f 100644
--- a/core/device/fd/fd.go
+++ b/core/device/fd/fd.go
@@ -1,3 +1,5 @@
 package fd
 
 const Driver = "fd"
+
+const defaultMTU = 1500
diff --git a/core/device/fd/fd_unix.go b/core/device/fd/fd_unix.go
index 7bce2a9..231a219 100644
--- a/core/device/fd/fd_unix.go
+++ b/core/device/fd/fd_unix.go
@@ -23,6 +23,9 @@ func Open(name string, mtu uint32) (device.Device, error) {
 	if err != nil {
 		return nil, fmt.Errorf("cannot open fd: %s", name)
 	}
+	if mtu == 0 {
+		mtu = defaultMTU
+	}
 	return open(fd, mtu)
 }