JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css">
<!-- Button trigger modal -->
<a href="https://www.google.com.br" data-toggle="modal" data-target="#exampleModal">
  Página 1
</a> |
<a href="https://www.bing.com" data-toggle="modal" data-target="#exampleModal">
  Página 2
</a>

<!-- Modal -->
<div class="modal fade" id="exampleModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true">
  <div class="modal-dialog" role="document">
    <div class="modal-content">
      <div class="modal-header">
        <h5 class="modal-title" id="exampleModalLabel">Modal title</h5>
        <button type="button" class="close" data-dismiss="modal" aria-label="Close">
          <span aria-hidden="true">&times;</span>
        </button>
      </div>
      <div class="modal-body">
        <div class="embed-responsive embed-responsive-16by9">
          <iframe id="iframeModal" class="embed-responsive-item" src=""></iframe>
        </div>
      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
        <button type="button" class="btn btn-primary">Save changes</button>
      </div>
    </div>
  </div>
</div>

JavaScript

$(document).on('click', 'a[data-toggle]', function (e) {
    e.preventDefault();

    //carrega URL do link no IFRAME
    $("#iframeModal").attr("src", this.href);
});