In some cases, packets are still not sent behind the router. I found that NuttX sends the ARP requests not to the router but to the target. Mistake in file net/route/netdev_router.c. From Aleksandr Kazantsev

fs/vfs/fs_stat.c

@@ -290,7 +290,7 @@ int inode_stat(FAR struct inode *inode, FAR struct stat *buf)
       else
 #endif
 #if defined(CONFIG_FS_SHM)
-       if (INODE_IS_SHM(inode)) */
+       if (INODE_IS_SHM(inode))
         {
           buf->st_mode = S_IFSHM;
         }