Angular 2, RC5 router-outlet inside another router-outlet

Although Modules are recommended they are optional for any route navigation.

You may configure routing like below without any modules.

app.routing

import { Routes, RouterModule }   from '@angular/router';

      import { DashboardComponent, 
         AdminComponent,
         ProfileComponent,
         UsersComponent
      } from './app.component';

      const appRoutes: Routes = [
      {
        path: '',
        redirectTo: '/dashboard/admin/users',
        pathMatch: 'full'
      },
      {
        path: 'dashboard',
        component: DashboardComponent,
        children:[
        {
         path : 'admin',
         component: AdminComponent,
         children:[
           {
            path : 'users',
            component: UsersComponent
           },
           {
            path : 'profile',
            component: ProfileComponent
           }
         ]
        }
       ]
     }
    ];

    export const routing = RouterModule.forRoot(appRoutes);

components

import { Component }          from '@angular/core';

@Component({
  selector: 'my-app',
  template: `
    <h3 class="title">Routing Deep dive</h3>
    <hr />
    <router-outlet></router-outlet>
  `
})
export class AppComponent {
}


@Component({
  template: `
    <h3 class="title">Dashboard</h3>
    <nav>
    </nav>
    <hr />
    <router-outlet></router-outlet>
  `
})
export class DashboardComponent {
}

@Component({
  template: `
    <h3 class="title">Admin</h3>
    <nav>
      <a routerLink="users" routerLinkActive="active" >Users</a>
      <a routerLink="profile" routerLinkActive="active" >Profile</a>
    </nav>
    <hr />
    <router-outlet></router-outlet>
  `
})
export class AdminComponent {
}

@Component({
  template: `
    <h3 class="title">Profile</h3>
  `
})
export class ProfileComponent {
}

@Component({
  template: `
    <h3 class="title">Users</h3>
    <hr />
  `
})
export class UsersComponent {
}

Here is the Plunker!!

Adding a solution with lazy loaded modules. This is a generic answer according to title and not to the body of the original question.

I created a separate module named UserCheckinModule for non-logged user containing Login and Signup pages/components as they usually share common design and functions/services.

Routes defined in app.routing.module.ts -

const routes: Routes = [
  { path: 'user', loadChildren: './user-checkin/user-checkin.module#UserCheckinModule' },
  { path: '**', redirectTo: 'user' }
];

Routes defined in user-checkin-routing.module.ts for UserCheckin module -

const routes: Routes = [
  {
    path: '',
    component: CheckinComponent, // base template component
    children: [
      { path: '', redirectTo: 'login' },
      { path: 'login', component: LoginComponent },
      { path: 'signup', component: SignupComponent },
      { path: '**', redirectTo: 'login' }
    ]
  }
];

Use forChild() in imports of user-checkin-routing.module.ts as

RouterModule.forChild(routes)

After this you will have to export your UserCheckinRoutingModule in UsercheckinModule. The app.component.html already contains a router-outlet and behaves as the base template/layout for the whole app. The UserCheckinModule is a child module and has its own routes and base template.

Content of checkin.component.html base template -

<router-outlet></router-outlet>