dropdown-toggle
はhref
を持っています。
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.0.0-alpha.6/css/bootstrap.min.css">
<div class="btn-group">
<a class="btn dropdown-toggle" data-toggle="dropdown" href="index.html">
Action
<span class="caret"></span>
</a>
<ul class="dropdown-menu">
<li><a href="#">Sub Link</a></li>
<li><a href="#">Sub Link</a></li>
</ul>
</div>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/4.0.0-alpha.6/js/bootstrap.min.js"></script>