in your component assign a variable like,
export class AppComponent {
netImage:any = "../assets/network.jpg";
title = 'app';
}
use this netImage in your src to get the image, as given below,
<figure class="figure">
<img [src]="netImage" class="figure-img img-fluid rounded" alt="A generic square placeholder image with rounded corners in a figure.">
<figcaption class="figure-caption">A caption for the above image.</figcaption>
</figure>