To add default redirect you need to use the redirectTo and pathMatch=full properties in the route object. Set the redirectTo to a some path that exist in your routes and set pathMatch to the full:
const routes: Routes = [
{ path: '', redirectTo: '/chat', pathMatch: 'full' },
{ path: 'chat', component: ChatContainerComponent }
];
In this example, you will be redirected to the chat route when visiting the main page /. If you enter any other URL, you will be redirected to the main page only.