diff --git a/boards/sim/sim/sim/src/sim_bringup.c b/boards/sim/sim/sim/src/sim_bringup.c
index cd3423e1ed3..3839a8bc8b7 100644
--- a/boards/sim/sim/sim/src/sim_bringup.c
+++ b/boards/sim/sim/sim/src/sim_bringup.c
@@ -118,6 +118,17 @@ int sim_bringup(void)
     }
 #endif
 
+#ifdef CONFIG_FS_TMPFS
+  /* Mount the tmpfs file system */
+
+  ret = mount(NULL, CONFIG_LIBC_TMPDIR, "tmpfs", 0, NULL);
+  if (ret < 0)
+    {
+      syslog(LOG_ERR, "ERROR: Failed to mount tmpfs at %s: %d\n",
+             CONFIG_LIBC_TMPDIR, ret);
+    }
+#endif
+
 #ifdef CONFIG_LIB_ZONEINFO_ROMFS
   /* Mount the TZ database */
 
diff --git a/net/route/Kconfig b/net/route/Kconfig
index 8c291a9edb6..1a937a2a5fb 100644
--- a/net/route/Kconfig
+++ b/net/route/Kconfig
@@ -112,7 +112,7 @@ config ROUTE_MAX_IPv6_RAMROUTES
 
 config ROUTE_FILEDIR
 	string "Routing table directory"
-	default /tmp
+	default LIBC_TMPDIR
 	depends on ROUTE_IPv4_FILEROUTE || ROUTE_IPv6_FILEROUTE
 	---help---
 		Provides the full path to location in the file system where routing