Yes, Daniel is correct, but to expand upon his answer, your primary app component would need to have a navbar component within it. That way, when you render the primary app (any page under the '/' path), it would also display the navbar. I am guessing that you wouldn't want your login page to display the navbar, so that shouldn't be a nested component, and should instead be by itself. So your routes would end up looking something like this:
<Router>
<Route path="/" component={App}>
<Route path="page1" component={Page1} />
<Route path="page2" component={Page2} />
</Route>
<Route path="/login" component={Login} />
</Router>
And the other components would look something like this:
var NavBar = React.createClass({
render() {
return (
<div>
<ul>
<a onClick={() => history.push('page1') }>Page 1</a>
<a onClick={() => history.push('page2') }>Page 2</a>
</ul>
</div>
)
}
});
var App = React.createClass({
render() {
return (
<div>
<NavBar />
<div>Other Content</div>
{this.props.children}
</div>
)
}
});