We want the path b to route to HelloBComponent inside the named router outlet o . This is the route configuration contained app.module.ts in within our Stackblitz demo.
const routes: Routes = [
{ path: 'a', component: HelloComponent },
{ path: 'b', outlet: 'o', component: HelloBComponent },
];
Approach
Configure the routerLink like this.
<button [routerLink]="[{ outlets: { o: ['b'] } }]">router link b</button>