JSF Regras de Navegação (Duvidas)

Pagina index.xhtml

<p:commandButton value="Entrar" id="start" type="submit" action="#{loginMB.autenticarUsuarioMB}"/>


<?xml version="1.0" encoding="UTF-8"?>

<faces-config
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-facesconfig_2_1.xsd"
    version="2.1">
	<managed-bean>
		<managed-bean-name>loginMB</managed-bean-name>
		<managed-bean-class>br.com.jrmassagem.bm.LoginMB</managed-bean-class>
		<managed-bean-scope>request</managed-bean-scope>
	</managed-bean>
	<navigation-rule>
		<display-name>index</display-name>
		<from-view-id>/index.xhtml</from-view-id>
		<navigation-case>
			<from-action>#{loginMB.autenticarUsuarioMB}</from-action>
			<from-outcome>loginErro</from-outcome>
			<to-view-id>/error/loginErro.xhtml</to-view-id>
		</navigation-case>
	</navigation-rule>
	<navigation-rule>
		<display-name>index</display-name>
		<from-view-id>/index.xhtml</from-view-id>
		<navigation-case>
			<from-action>#{loginMB.autenticarUsuarioMB}</from-action>
			<from-outcome>menu</from-outcome>
			<to-view-id>/pages/menu.xhtml</to-view-id>
		</navigation-case>
	</navigation-rule>
 </faces-config>


Classe LoginMB

@SuppressWarnings("rawtypes")
	public String autenticarUsuarioMB() throws DAOException {
	    boolean auth = DAOFactory.getInstance().getLoginDAOImpl().autenticarUsuarioHb(login);
	    if (auth) {
			FacesContext ctx = FacesContext.getCurrentInstance();
			Map clienteSession = ctx.getExternalContext().getSessionMap();
			clienteSession.put("nome",login.getTxtNome());
			clienteSession.put("perfil",login.getTxtPerfil());
			this.login.setTxtNome(clienteSession.get("nome").toString());
	    	return MENU;
	    }else{
	    	 return LOGIN_ERRO;
	    }
	    
	}