Angular 4: Routing

// creamos por ejemplo tres componentes
ng generate component Uno
ng generate component Dos
ng generate component Tres

En app.component.html:
...
<router-outlet></router-outlet>

En app.module.ts:
const appRoutes: Routes = [
  { path: '', redirectTo: 'uno', pathMatch: 'full' },
  { path: 'uno', component: UnoComponent },
  { path: 'dos', component: DosComponent },
  { path: 'tres', component: TresComponent }
];
...
imports: [
    BrowserModule,
    RouterModule.forRoot(appRoutes)
  ],

Para probarlo:
http://localhost:4200/
http://localhost:4200/uno
http://localhost:4200/dos
http://localhost:4200/tres