in layout/default.ctp i done code like this but working fine page but in Dashboard link was not working but shows on move over i found the url
<?php if ($this->Session->read('Auth.User')): ?>
<?php echo $this->Html->link('Dashboard','/Dashboard/index', array('controller' => 'Dashboard', 'action' => 'index','class'=>'classname')); ?>
<?php echo $this->Html->link('logout','/users/logout', array('controller' => 'users', 'action' => 'logout','class'=>'classname')); ?>
<?php else: ?>
<?php echo $this->Html->link('Register', '/users/add',array('controller' => 'users', 'action' => 'add','class'=>'classname')); ?>
<?php echo $this->Html->link('login', '/users/login',array('controller' => 'users', 'action' => 'login','class'=>'classname')); ?>
<?php endif; ?>