Angular 2 module lazy-loading not working

I'm trying to get my head around Angular 2 (RC5) lazy-loading of modules by building a basic structure of a site with two sections, welcome and backend (think login page and main site). I've set it up following the Angular 2 docs on feature modules, one for the welcome section and one for the backend. It correctly defaults to the welcome component but my button in the welcome component that's supposed to link to the 'backend' route goes to 'welcome/backend' instead. Typing in the url with just /backend goes to /backend/welcome. Here's my app.routing.ts file:

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

export const routes: Routes = [
  { path: '', redirectTo: 'welcome', pathMatch: 'full'},
  { path: 'backend', loadChildren: 'app/backend/backend.module' }
];

export const routing = RouterModule.forRoot(routes);

And my welcome.routing.ts:

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

import { WelcomeComponent } from './welcome.component';

export const routing = RouterModule.forChild([
    { path: 'welcome', component: WelcomeComponent}
]);

And my welcome.component.ts:

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

@Component({
    template: `
        <h2>Welcome</h2>
        <nav><a routerLink="backend">Login</a></nav>
    `
})
export class WelcomeComponent { }

Anyway, here's plunk of the whole app to make it easier Plunkr. The ones that matter are in welcome and backend folders. Clicking Login should show Backend with a Logout button which takes you back to the Welcome page.

Any suggestions would be appreciated.

I finally go it working by figuring out that router stacks routes from nested modules (e.g. 'backend' route in app.routing and 'backend' in backend.routing results in '/backend/backend' as the url). So the solution was to have a backend.routing.ts with a single route of { path: '', component: BackendComponent }. It was also necessary to add a / to the routerLink values (e.g. /backend instead of backend). Here's my final backend.routing.ts:

import { Routes, RouterModule }  from '@angular/router';
import { BackendComponent }    from './backend.component';

const routes: Routes = [
    { path: '', component: BackendComponent }
];

export const routing = RouterModule.forChild(routes);

And backend.module.ts:

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { BackendComponent } from './backend.component';
import { routing } from './backend.routing';

@NgModule({
    imports: [ routing ],
    declarations: [ BackendComponent ]
})
export default class BackendModule { }

welcome.component.ts:

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

@Component({
    template: `
        <h2>Welcome</h2>
        <nav><a routerLink="backend">Login</a></nav>
    `
})
export class WelcomeComponent { }

backend.component.ts

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

@Component({
    template: `
        <h2>Backend</h2>
        <nav><a routerLink="welcome">Logout</a></nav>
    `
})
export class BackendComponent { }

This resulted in the login button taking me to /backend and the logout button taking me to /welcome as expected. Here's a link to the plunk: Plunker