diff --git a/core/lib/Drupal/Core/Menu/MenuLinkManager.php b/core/lib/Drupal/Core/Menu/MenuLinkManager.php
index 3647e07..c307ecd 100644
--- a/core/lib/Drupal/Core/Menu/MenuLinkManager.php
+++ b/core/lib/Drupal/Core/Menu/MenuLinkManager.php
@@ -12,9 +12,11 @@
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Component\Utility\String;
 use Drupal\Core\Extension\ModuleHandlerInterface;
+use Drupal\Core\Plugin\ModuleDependencyTrait;
 use Drupal\Core\Plugin\Discovery\ContainerDerivativeDiscoveryDecorator;
 use Drupal\Core\Plugin\Discovery\YamlDiscovery;
 use Drupal\Core\Plugin\Factory\ContainerFactory;
+use Symfony\Component\Routing\RouteCollection;
 
 
 /**
@@ -24,6 +26,8 @@
  */
 class MenuLinkManager implements MenuLinkManagerInterface {
 
+  use ModuleDependencyTrait;
+
   /**
    * Provides some default values for the definition of all menu link plugins.
    *
@@ -104,7 +108,6 @@ class MenuLinkManager implements MenuLinkManagerInterface {
    */
   protected $moduleHandler;
 
-
   /**
    * Constructs a \Drupal\Core\Menu\MenuLinkManager object.
    *
@@ -183,6 +186,29 @@ public function getDefinitions() {
         unset($definitions[$plugin_id]);
       }
     }
+
+    // Filter out definitions with unmet module dependencies.
+    $this->filterByModuleDependencies($definitions);
+
+    // Also filter by the unmet route dependencies.
+    $routeDiscovery = new YamlDiscovery('routing', $this->moduleHandler->getModuleDirectories());
+    $route_definitions = $routeDiscovery->getDefinitions();
+    foreach ($definitions as $plugin_id => $plugin_definition) {
+      $route_name = $plugin_definition['route_name'];
+      if (!empty($route_definitions[$route_name]) && !empty($route_definitions[$route_name]['requirements']) && !empty($route_definitions[$route_name]['requirements']['_module_dependencies'])) {
+        if ($modules = $route_definitions[$route_name]['requirements']['_module_dependencies']) {
+          $explode_and = $this->explodeString($modules, '+');
+          foreach ($explode_and as $module) {
+            // If any moduleExists() call returns FALSE, remove the menu and
+            // move on to the next.
+            if (!$this->moduleHandler->moduleExists($module)) {
+              unset($definitions[$plugin_id]);
+            }
+          }
+        }
+      }
+    }
+
     return $definitions;
   }
 
diff --git a/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php b/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php
index 5828d33..c94356b 100644
--- a/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php
+++ b/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php
@@ -27,6 +27,7 @@
 class DefaultPluginManager extends PluginManagerBase implements PluginManagerInterface, CachedDiscoveryInterface {
 
   use DiscoveryCachedTrait;
+  use ModuleDependencyTrait;
 
   /**
    * Cache backend instance.
@@ -239,6 +240,9 @@ protected function findDefinitions() {
         unset($definitions[$plugin_id]);
       }
     }
+
+    $this->filterByModuleDependencies($definitions);
+
     return $definitions;
   }
 
diff --git a/core/lib/Drupal/Core/Plugin/ModuleDependencyTrait.php b/core/lib/Drupal/Core/Plugin/ModuleDependencyTrait.php
new file mode 100644
index 0000000..8bc5266
--- /dev/null
+++ b/core/lib/Drupal/Core/Plugin/ModuleDependencyTrait.php
@@ -0,0 +1,105 @@
+<?php
+
+/**
+ * @file
+ * Contains Drupal\Core\Plugin\ModuleDependencyTrait.
+ */
+
+namespace Drupal\Core\Plugin;
+
+use Drupal\Core\Extension\ModuleHandlerInterface;
+
+/**
+ * Provides a trait for checking the module dependencies of a plugin.
+ */
+trait ModuleDependencyTrait {
+
+  /**
+   * Filter out definitions with unmet module dependencies.
+   *
+   * @param array $definitions
+   *   An array of the available plugin definitions.
+   */
+  protected function filterByModuleDependencies(array &$definitions) {
+    foreach ($definitions as $plugin_id => &$definition) {
+      if (isset($definition['module_dependencies'])) {
+        if (($this->checkModuleDependencies($definition['module_dependencies'])) == FALSE) {
+          unset($definitions[$plugin_id]);
+        }
+      }
+    }
+  }
+
+  /**
+   * Checks whether module dependencies are satisfied.
+   *
+   * @param string $modules
+   *   The list of required modules, separated by a '+' (AND) or ','' (OR).
+   *
+   * @return bool
+   *   TRUE if the dependencies are satisfied, FALSE otherwise.
+   */
+  protected function checkModuleDependencies($modules) {
+    $explode_and = is_array($modules) ? $modules : $this->explodeString($modules, '+');
+    if (count($explode_and) > 1) {
+      foreach ($explode_and as $module) {
+        if (!$this->getModuleHandler()->moduleExists($module)) {
+          return FALSE;
+        }
+      }
+      return TRUE;
+    }
+    else {
+      // OR condition, exploding on ',' character.
+      foreach ($this->explodeString($modules, ',') as $module) {
+        if ($this->getModuleHandler()->moduleExists($module)) {
+          return TRUE;
+        }
+      }
+      return FALSE;
+    }
+  }
+
+  /**
+   * Explodes a string based on a separator.
+   *
+   * @param string $string
+   *   The string to explode.
+   * @param string $separator
+   *   The string separator to explode with.
+   *
+   * @return array
+   *   An array of exploded (and trimmed) values.
+   */
+  protected function explodeString($string, $separator = ',') {
+    return array_filter(array_map('trim', explode($separator, $string)));
+  }
+
+  /**
+   * Returns the module handler.
+   *
+   * @return \Drupal\Core\Extension\ModuleHandlerInterface
+   *   The module handler.
+   */
+  protected function getModuleHandler() {
+    if (!$this->moduleHandler) {
+      $this->moduleHandler = \Drupal::moduleHandler();
+    }
+    return $this->moduleHandler;
+  }
+
+  /**
+   * Sets the module handler.
+   *
+   * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
+   *   The module handler.
+   *
+   * @return $this
+   */
+  public function setModuleHandler(ModuleHandlerInterface $module_handler) {
+    $this->moduleHandler = $module_handler;
+
+    return $this;
+  }
+
+}
diff --git a/core/modules/forum/src/Access/RouteProcessor.php b/core/modules/forum/src/Access/RouteProcessor.php
new file mode 100644
index 0000000..a6f0bab
--- /dev/null
+++ b/core/modules/forum/src/Access/RouteProcessor.php
@@ -0,0 +1,61 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\forum\Access\RouteProcessor.
+ */
+
+namespace Drupal\forum\Access;
+
+use Drupal\Core\Config\ConfigFactoryInterface;
+use Drupal\Core\Entity\EntityManagerInterface;
+use Drupal\Core\RouteProcessor\OutboundRouteProcessorInterface;
+use Symfony\Component\Routing\Route;
+
+/**
+ * Processes the inbound path by resolving it to the forum page.
+ */
+class RouteProcessor implements OutboundRouteProcessorInterface {
+
+  /**
+   * The config factory.
+   *
+   * @var \Drupal\Core\Config\ConfigFactoryInterface
+   */
+  protected $configFactory;
+
+  /**
+   * Entity manager service.
+   *
+   * @var \Drupal\Core\Entity\EntityManagerInterface
+   */
+  protected $entityManager;
+
+  /**
+   * Constructs a RouteProcessor object.
+   *
+   * @param \Drupal\Core\Config\ConfigFactoryInterface $config_factory
+   *   The config factory.
+   * @param \Drupal\Core\Entity\EntityManagerInterface $entity_manager
+   *   The entity manager service.
+   */
+  function __construct(ConfigFactoryInterface $config_factory, EntityManagerInterface $entity_manager) {
+    $this->configFactory = $config_factory;
+    $this->entityManager = $entity_manager;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function processOutbound($route_name, Route $route, array &$parameters) {
+    if ($route_name == 'entity.taxonomy_term.canonical' && !empty($parameters['taxonomy_term'])) {
+      // Take over URI construction for taxonomy terms that belongs to forum.
+      if ($vid = $this->configFactory->get('forum.settings')->get('vocabulary')) {
+        if ($this->entityManager->getStorage('taxonomy_term')->load($parameters['taxonomy_term'])->getVocabularyId() == $vid) {
+          $route->setPath('/forum/{taxonomy_term}');
+        }
+      }
+    }
+  }
+
+}
diff --git a/core/modules/system/src/Tests/Menu/MenuLinkDependencyTest.php b/core/modules/system/src/Tests/Menu/MenuLinkDependencyTest.php
new file mode 100644
index 0000000..f8c69c1
--- /dev/null
+++ b/core/modules/system/src/Tests/Menu/MenuLinkDependencyTest.php
@@ -0,0 +1,56 @@
+<?php
+
+/**
+ * @file
+ * Definition of Drupal\system\Tests\Menu\MenuLinkDependencyTest.
+ */
+
+namespace Drupal\system\Tests\Menu;
+
+use Drupal\simpletest\KernelTestBase;
+
+/**
+ * Tests menu router and default menu link functionality.
+ *
+ * @group Menu
+ */
+class MenuLinkDependencyTest extends KernelTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = ['menu_dependency_test'];
+
+  /**
+   * Test menu link dependencies.
+   */
+  public function testMenuLinkDependency() {
+    /** @var \Drupal\Core\Menu\MenuLinkManagerInterface $menu_link_manager */
+    $menu_link_manager = \Drupal::service('plugin.manager.menu.link');
+    $definitions = $menu_link_manager->getDefinitions();
+    $this->assertTrue(empty($definitions['menu_dependency_test.dependency']), 'A menu link with unmet dependencies is not found.');
+
+    \Drupal::service('module_installer')->install(['system', 'menu_ui']);
+    $menu_link_manager = \Drupal::service('plugin.manager.menu.link');
+    $definitions = $menu_link_manager->getDefinitions();
+    $this->assertTrue(!empty($definitions['menu_dependency_test.dependency']), 'Menu link is found when the dependent module is enabled.');
+  }
+
+  /**
+   * Test route dependencies.
+   */
+  public function testMenuLinkRouteDependency() {
+    /** @var \Drupal\Core\Menu\MenuLinkManagerInterface $menu_link_manager */
+    $menu_link_manager = \Drupal::service('plugin.manager.menu.link');
+    $definitions = $menu_link_manager->getDefinitions();
+    $this->assertTrue(empty($definitions['menu_dependency_test.route_dependency']), 'A menu link with route unmet dependencies is not found.');
+
+    \Drupal::service('module_installer')->install(['system', 'menu_ui']);
+    $menu_link_manager = \Drupal::service('plugin.manager.menu.link');
+    $definitions = $menu_link_manager->getDefinitions();
+    $this->assertTrue(!empty($definitions['menu_dependency_test.route_dependency']), 'Menu link route is found when the dependent module is enabled.');
+  }
+
+}
diff --git a/core/modules/system/tests/modules/menu_dependency_test/menu_dependency_test.info.yml b/core/modules/system/tests/modules/menu_dependency_test/menu_dependency_test.info.yml
new file mode 100644
index 0000000..a9edd5c
--- /dev/null
+++ b/core/modules/system/tests/modules/menu_dependency_test/menu_dependency_test.info.yml
@@ -0,0 +1,6 @@
+name: 'Menu dependency tests'
+type: module
+description: 'Support module for menu dependency testing.'
+package: Testing
+version: VERSION
+core: 8.x
diff --git a/core/modules/system/tests/modules/menu_dependency_test/menu_dependency_test.links.menu.yml b/core/modules/system/tests/modules/menu_dependency_test/menu_dependency_test.links.menu.yml
new file mode 100644
index 0000000..cc097f9
--- /dev/null
+++ b/core/modules/system/tests/modules/menu_dependency_test/menu_dependency_test.links.menu.yml
@@ -0,0 +1,8 @@
+menu_dependency_test.dependency:
+  title: 'Test menu link dependencies'
+  route_name: menu_dependency_test.menu_dependency_test
+  module_dependencies: 'menu_ui'
+
+menu_dependency_test.route_dependency:
+  title: 'Test menu link dependencies'
+  route_name: menu_dependency_test.menu_dependency_route_test
diff --git a/core/modules/system/tests/modules/menu_dependency_test/menu_dependency_test.routing.yml b/core/modules/system/tests/modules/menu_dependency_test/menu_dependency_test.routing.yml
new file mode 100644
index 0000000..19bf39b
--- /dev/null
+++ b/core/modules/system/tests/modules/menu_dependency_test/menu_dependency_test.routing.yml
@@ -0,0 +1,14 @@
+menu_dependency_test.menu_dependency_test:
+  path: '/menu-dependency-test/dependency'
+  defaults:
+    _content: '\Drupal\menu_dependency_test\Controller\MenuDependencyTestController::menuDependencyTestCallback'
+  requirements:
+    _access: 'TRUE'
+
+menu_dependency_test.menu_dependency_route_test:
+  path: '/menu-dependency-test/route-dependency'
+  defaults:
+    _content: '\Drupal\menu_dependency_test\Controller\MenuDependencyTestController::menuDependencyTestCallback'
+  requirements:
+    _access: 'TRUE'
+    _module_dependencies: 'menu_ui'
diff --git a/core/modules/system/tests/modules/menu_dependency_test/src/Controller/MenuDependencyTestController.php b/core/modules/system/tests/modules/menu_dependency_test/src/Controller/MenuDependencyTestController.php
new file mode 100644
index 0000000..9729a20
--- /dev/null
+++ b/core/modules/system/tests/modules/menu_dependency_test/src/Controller/MenuDependencyTestController.php
@@ -0,0 +1,23 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\menu_dependency_test\Controller\MenuDependencyTestController.
+ */
+
+namespace Drupal\menu_dependency_test\Controller;
+use Drupal\Core\Controller\ControllerBase;
+
+/**
+ * Controller routines for menu_dependency_test routes.
+ */
+class MenuDependencyTestController extends ControllerBase {
+
+  /**
+   * Callback for menu_dependency_test routes.
+   */
+  public function menuDependencyTestCallback() {
+    return $this->t('Menu dependency test callback.');
+  }
+
+}
diff --git a/core/tests/Drupal/Tests/Core/Plugin/ModuleDependencyTraitTest.php b/core/tests/Drupal/Tests/Core/Plugin/ModuleDependencyTraitTest.php
new file mode 100644
index 0000000..8bf4d4a
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/Plugin/ModuleDependencyTraitTest.php
@@ -0,0 +1,92 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Tests\Core\Plugin\ModuleDependencyTraitTest.
+ */
+
+namespace Drupal\Tests\Core\Plugin;
+
+use Drupal\Core\Plugin\ModuleDependencyTrait;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * Tests the module dependency trait.
+ *
+ * @group Plugin
+ *
+ * @coversDefaultClass \Drupal\Core\Plugin\ModuleDependencyTrait
+ */
+class ModuleDependencyTraitTest extends UnitTestCase {
+
+  /**
+   * Tests the filtering.
+   *
+   * @covers ::filterByModuleDependencies
+   * @covers ::checkModuleDependencies
+   * @covers ::explodeString
+   * @covers ::getModuleHandler
+   * @covers ::setModuleHandler
+   */
+  public function testFilterByModuleDependencies() {
+    $module_handler = $this->getMock('Drupal\Core\Extension\ModuleHandlerInterface');
+    $module_handler->expects($this->any())
+      ->method('moduleExists')
+      ->willReturnMap([
+        ['existing_module', TRUE],
+        ['existing_module2', TRUE],
+        ['not_existing_module', FALSE],
+      ]);
+
+    $test_plugin_manager = new ModuleDependencyTestPluginManager();
+    $test_plugin_manager->setModuleHandler($module_handler);
+
+    $test_definition = [];
+    // Just a single module dependency.
+    $test_definition['plugin_1'] = [
+      'id' => 'plugin_1',
+      'provider' => 'test_module',
+      'module_dependencies' => 'existing_module'
+    ];
+    // Multiple connected via AND.
+    $test_definition['plugin_2'] = [
+      'id' => 'plugin_2',
+      'provider' => 'test_module',
+      'module_dependencies' => 'existing_module+existing_module2',
+    ];
+    // An array of module dependencies.
+    $test_definition['plugin_3'] = [
+      'id' => 'plugin_3',
+      'provider' => 'test_module',
+      'module_dependencies' => ['existing_module', 'existing_module2']
+    ];
+    // One missing module.
+    $test_definition['plugin_4'] = [
+      'id' => 'plugin_4',
+      'provider' => 'test_module',
+      'module_dependencies' => 'existing_module+not_existing_module',
+    ];
+    // Multiple connected via OR.
+    $test_definition['plugin_5'] = [
+      'id' => 'plugin_5',
+      'provider' => 'test_module',
+      'module_dependencies' => 'existing_module,not_existing_module',
+    ];
+
+    $test_plugin_manager->runFilterByModuleDependencies($test_definition);
+
+    $this->assertCount(4, $test_definition);
+    $this->assertEquals(['plugin_1', 'plugin_2', 'plugin_3', 'plugin_5'], array_keys($test_definition));
+  }
+
+}
+
+class ModuleDependencyTestPluginManager {
+
+  use ModuleDependencyTrait;
+
+  public function runFilterByModuleDependencies(array &$definitions) {
+    return $this->filterByModuleDependencies($definitions);
+  }
+
+}