var frameSrc = "/login";

$('#openBtn').click(function(){     $('#myModal').on('show', function () {

        $('iframe').attr("src",frameSrc);        });     $('#myModal').modal({show:true}) });

 

<a id="openBtn" class="btn" href="#">Open modal</a>

<div id="myModal" class="modal hide fade" role="dialog" tabIndex="-1">  <div class="modal-header">   <button class="close" type="button" data-dismiss="modal">×</button>    <h3>Dialog</h3>  </div>  <div class="modal-body">       <iframe style="zoom: 0.6;" height="250" src="" frameBorder="0" width="99.6%"></iframe>  </div>  <div class="modal-footer">   <button class="btn" data-dismiss="modal">OK</button>  </div> </div>