diff --git a/portnums.proto b/portnums.proto
index dd8a7c6..ab806ad 100644
--- a/portnums.proto
+++ b/portnums.proto
@@ -133,6 +133,12 @@ enum PortNum {
    */
   SIMULATOR_APP = 69;
 
+  /*
+   * Provides a traceroute functionality to show the route a packet towards
+   * a certain destination would take on the mesh.
+   */
+  TRACEROUTE_APP = 70;
+
   /*
    * Private applications should use portnums >= 256.
    * To simplify initial development and testing you can use "PRIVATE_APP"