<div class="caja caja-sombra">
<h2>Ejemplo 6</h2>
<p>Sombra interior exterior</p>
</div>

CSS

.caja{
 width: 200px;
 height: 150px;
 background-color: #f4f4f4;
 border-radius: 5px / 100px;
 border: 1px dotted #9C9C9C;
 box-shadow: inset 0 4px 6px rgba(0,0,0,.5);
}
.caja-sombra{
    position: relative;
    float: left;
    padding: 1em;
    margin: 100px 50px;
    
}
.caja-sombra:before, .caja-sombra:after{
    content: "";
    position: absolute;
    z-index: -2;
}
.sombra1:beforez{
    top: 10px;
    bottom: 10px;
    left: 0;
    right: 50%;
    box-shadow: 0 0 15px rgba(0,0,0,0.6);
   
}
.sombra2:before{
    right: 0
}