Mikrotik routerboard 1000 outdoor type have USB port that’s why it possible to use 3G cellular connection so i thought is it possible to use redundancy? If primary port down, switch to 3G connection automatically.
There is nothing built-in to do this automatically. You must write your own scripts to switch between various connections when 1 or the other goes down.
It`s simple. You can use routing distance value. Add both default routes with different distance. Route with low distance will be work. Additionally you can enable ping-check on routes. Good luck