<!-- default nav -->
<nav class="nav">
  <a class="nav-link active" href="#">Active</a>
  <a class="nav-link" href="#">Link</a>
  <a class="nav-link" href="#">Link</a>
  <a class="nav-link disabled" href="#">Disabled</a>
</nav>

<!-- vertical nav -->
<nav class="nav flex-column">
  ...
</nav>