angular 2 webpack-dev-server，路由不工作

import { RouterModule, Routes } from '@angular/router';
import { HomeComponent } from './home.component';
import { AboutComponent } from './about.component';

const routes: Routes = [
  { path: '', component: HomeComponent },
  { path: 'about', component: AboutComponent }
];

@NgModule({
  imports: [RouterModule.forRoot(routes)],
  exports: [RouterModule]
})
export class AppRoutingModule { }

<router-outlet></router-outlet>

<a routerLink="/">Home</a>
<a routerLink="/about">About</a>

import { AppRoutingModule } from './app-routing.module';

@NgModule({
  imports: [
    BrowserModule,
    AppRoutingModule
  ],
  declarations: [AppComponent],
  bootstrap: [AppComponent]
})
export class AppModule { }