diff --git a/library/Icingadb/Model/Dependency.php b/library/Icingadb/Model/Dependency.php
new file mode 100644
index 000000000..0a32a8096
--- /dev/null
+++ b/library/Icingadb/Model/Dependency.php
@@ -0,0 +1,95 @@
+<?php
+
+/* Icinga DB Web | (c) 2024 Icinga GmbH | GPLv2 */
+
+namespace Icinga\Module\Icingadb\Model;
+
+use Icinga\Module\Icingadb\Model\Behavior\Bitmask;
+use ipl\Orm\Behavior\Binary;
+use ipl\Orm\Behavior\BoolCast;
+use ipl\Orm\Behaviors;
+use ipl\Orm\Model;
+use ipl\Orm\Query;
+use ipl\Orm\Relations;
+
+/**
+ * Dependency model.
+ *
+ * @property string $id
+ * @property string $name
+ * @property string $display_name
+ * @property ?string $redundancy_group_id
+ * @property bool $disable_checks
+ * @property bool $disable_notifications
+ * @property bool $ignore_soft_states
+ * @property ?string $timeperiod_id
+ * @property string[] $states
+ *
+ * @property (?Timeperiod)|Query $timeperiod
+ * @property (?RedundancyGroup)|Query $redundancy_group
+ * @property (?DependencyState)|Query $state
+ * @property DependencyEdge|Query $edge
+ */
+class Dependency extends Model
+{
+    public function getTableName(): string
+    {
+        return 'dependency';
+    }
+
+    public function getKeyName(): string
+    {
+        return 'id';
+    }
+
+    public function getColumns(): array
+    {
+        return [
+            'name',
+            'display_name',
+            'redundancy_group_id',
+            'disable_checks',
+            'disable_notifications',
+            'ignore_soft_states',
+            'timeperiod_id',
+            'states'
+        ];
+    }
+
+    public function createBehaviors(Behaviors $behaviors): void
+    {
+        $behaviors->add(new Binary([
+            'id',
+            'redundancy_group_id',
+            'timeperiod_id'
+        ]));
+        $behaviors->add(new BoolCast([
+            'disable_checks',
+            'disable_notifications',
+            'ignore_soft_states'
+        ]));
+        $behaviors->add(new Bitmask([
+            'states' => [
+                'ok'        => 1,
+                'warning'   => 2,
+                'critical'  => 4,
+                'unknown'   => 8,
+                'up'        => 16,
+                'down'      => 32
+            ],
+        ]));
+    }
+
+    public function createRelations(Relations $relations): void
+    {
+        $relations->belongsTo('timeperiod', Timeperiod::class)
+            ->setJoinType('LEFT');
+        $relations->belongsTo('redundancy_group', RedundancyGroup::class)
+            ->setJoinType('LEFT');
+
+        $relations->hasOne('state', DependencyState::class)
+            ->setJoinType('LEFT');
+
+        $relations->hasOne('edge', DependencyEdge::class);
+    }
+}
diff --git a/library/Icingadb/Model/DependencyEdge.php b/library/Icingadb/Model/DependencyEdge.php
new file mode 100644
index 000000000..d6c6599c2
--- /dev/null
+++ b/library/Icingadb/Model/DependencyEdge.php
@@ -0,0 +1,63 @@
+<?php
+
+/* Icinga DB Web | (c) 2024 Icinga GmbH | GPLv2 */
+
+namespace Icinga\Module\Icingadb\Model;
+
+use ipl\Orm\Behavior\Binary;
+use ipl\Orm\Behaviors;
+use ipl\Orm\Model;
+use ipl\Orm\Query;
+use ipl\Orm\Relations;
+
+/**
+ * Dependency edge model.
+ *
+ * @property string $to_node_id
+ * @property string $from_node_id
+ * @property ?string $dependency_id
+ *
+ * @property DependencyNode|Query $from
+ * @property DependencyNode|Query $to
+ * @property (?Dependency)|Query $dependency
+ */
+class DependencyEdge extends Model
+{
+    public function getTableName(): string
+    {
+        return 'dependency_edge';
+    }
+
+    public function getKeyName(): array
+    {
+        return ['to_node_id', 'from_node_id'];
+    }
+
+    public function getColumns(): array
+    {
+        return [
+            'to_node_id',
+            'from_node_id',
+            'dependency_id'
+        ];
+    }
+
+    public function createBehaviors(Behaviors $behaviors): void
+    {
+        $behaviors->add(new Binary([
+            'to_node_id',
+            'from_node_id',
+            'dependency_id'
+        ]));
+    }
+
+    public function createRelations(Relations $relations): void
+    {
+        $relations->belongsTo('from', DependencyNode::class)
+            ->setCandidateKey('from_node_id');
+        $relations->belongsTo('to', DependencyNode::class)
+            ->setCandidateKey('to_node_id');
+        $relations->belongsTo('dependency', Dependency::class)
+            ->setJoinType('LEFT');
+    }
+}
diff --git a/library/Icingadb/Model/DependencyNode.php b/library/Icingadb/Model/DependencyNode.php
new file mode 100644
index 000000000..995e9be7e
--- /dev/null
+++ b/library/Icingadb/Model/DependencyNode.php
@@ -0,0 +1,88 @@
+<?php
+
+/* Icinga DB Web | (c) 2024 Icinga GmbH | GPLv2 */
+
+namespace Icinga\Module\Icingadb\Model;
+
+use ipl\Orm\Behavior\Binary;
+use ipl\Orm\Behaviors;
+use ipl\Orm\Model;
+use ipl\Orm\Query;
+use ipl\Orm\Relations;
+
+/**
+ * Dependency node model.
+ *
+ * @property string $id
+ * @property ?string $host_id
+ * @property ?string $service_id
+ * @property ?string $redundancy_group_id
+ *
+ * @property (?Host)|Query $host
+ * @property (?Service)|Query $service
+ * @property (?RedundancyGroup)|Query $redundancy_group
+ * @property (?DependencyEdge)|Query $from
+ * @property (?DependencyEdge)|Query $to
+ * @property (?DependencyNode)|Query $child
+ * @property (?DependencyNode)|Query $parent
+ */
+class DependencyNode extends Model
+{
+    public function getTableName(): string
+    {
+        return 'dependency_node';
+    }
+
+    public function getKeyName(): string
+    {
+        return 'id';
+    }
+
+    public function getColumns(): array
+    {
+        return [
+            'id',
+            'host_id',
+            'service_id',
+            'redundancy_group_id'
+        ];
+    }
+
+    public function createBehaviors(Behaviors $behaviors): void
+    {
+        $behaviors->add(new Binary([
+            'id',
+            'host_id',
+            'service_id',
+            'redundancy_group_id'
+        ]));
+    }
+
+    public function createRelations(Relations $relations): void
+    {
+        $relations->belongsTo('host', Host::class)
+            ->setJoinType('LEFT');
+        $relations->belongsTo('service', Service::class)
+            ->setJoinType('LEFT');
+        $relations->belongsTo('redundancy_group', RedundancyGroup::class)
+            ->setJoinType('LEFT');
+
+        $relations->hasMany('from', DependencyEdge::class)
+            ->setForeignKey('from_node_id')
+            ->setJoinType('LEFT');
+        $relations->hasMany('to', DependencyEdge::class)
+            ->setForeignKey('to_node_id')
+            ->setJoinType('LEFT');
+
+        $relations->belongsToMany('child', self::class)
+            ->through(DependencyEdge::class)
+            ->setForeignKey('to_node_id')
+            ->setTargetForeignKey('from_node_id')
+            ->setJoinType('LEFT');
+        $relations->belongsToMany('parent', self::class)
+            ->through(DependencyEdge::class)
+            ->setForeignKey('from_node_id')
+            ->setTargetForeignKey('to_node_id')
+            ->setJoinType('LEFT');
+    }
+}
diff --git a/library/Icingadb/Model/DependencyState.php b/library/Icingadb/Model/DependencyState.php
new file mode 100644
index 000000000..cf1eb5de0
--- /dev/null
+++ b/library/Icingadb/Model/DependencyState.php
@@ -0,0 +1,58 @@
+<?php
+
+/* Icinga DB Web | (c) 2024 Icinga GmbH | GPLv2 */
+
+namespace Icinga\Module\Icingadb\Model;
+
+use ipl\Orm\Behavior\Binary;
+use ipl\Orm\Behavior\BoolCast;
+use ipl\Orm\Behaviors;
+use ipl\Orm\Model;
+use ipl\Orm\Query;
+use ipl\Orm\Relations;
+
+/**
+ * Dependency state model.
+ *
+ * @property string $id
+ * @property string $dependency_id
+ * @property bool $failed
+ *
+ * @property Dependency|Query $dependency
+ */
+class DependencyState extends Model
+{
+    public function getTableName(): string
+    {
+        return 'dependency_state';
+    }
+
+    public function getKeyName(): string
+    {
+        return 'id';
+    }
+
+    public function getColumns(): array
+    {
+        return [
+            'dependency_id',
+            'failed'
+        ];
+    }
+
+    public function createBehaviors(Behaviors $behaviors): void
+    {
+        $behaviors->add(new Binary([
+            'id',
+            'dependency_id'
+        ]));
+        $behaviors->add(new BoolCast([
+            'failed'
+        ]));
+    }
+
+    public function createRelations(Relations $relations): void
+    {
+        $relations->belongsTo('dependency', Dependency::class);
+    }
+}
diff --git a/library/Icingadb/Model/Host.php b/library/Icingadb/Model/Host.php
index c6979839e..a68275950 100644
--- a/library/Icingadb/Model/Host.php
+++ b/library/Icingadb/Model/Host.php
@@ -181,6 +181,8 @@ public function createBehaviors(Behaviors $behaviors)
         ]));
 
         $behaviors->add(new ReRoute([
+            'child'         => 'dependency_node.child',
+            'parent'        => 'dependency_node.parent',
             'servicegroup'  => 'service.servicegroup',
             'user'          => 'notification.user',
             'usergroup'     => 'notification.usergroup'
@@ -235,6 +237,8 @@ public function createDefaults(Defaults $defaults)
 
     public function createRelations(Relations $relations)
     {
+        $relations->belongsTo('dependency_node', DependencyNode::class)
+            ->setJoinType('LEFT');
         $relations->belongsTo('environment', Environment::class);
         $relations->belongsTo('eventcommand', Eventcommand::class);
         $relations->belongsTo('checkcommand', Checkcommand::class);
diff --git a/library/Icingadb/Model/RedundancyGroup.php b/library/Icingadb/Model/RedundancyGroup.php
new file mode 100644
index 000000000..c8a76e7bf
--- /dev/null
+++ b/library/Icingadb/Model/RedundancyGroup.php
@@ -0,0 +1,67 @@
+<?php
+
+/* Icinga DB Web | (c) 2024 Icinga GmbH | GPLv2 */
+
+namespace Icinga\Module\Icingadb\Model;
+
+use Icinga\Module\Icingadb\Model\Behavior\ReRoute;
+use ipl\Orm\Behavior\Binary;
+use ipl\Orm\Behavior\BoolCast;
+use ipl\Orm\Behaviors;
+use ipl\Orm\Model;
+use ipl\Orm\Query;
+use ipl\Orm\Relations;
+
+/**
+ * Redundancy group model.
+ *
+ * @property string $id
+ * @property string $name
+ * @property string $display_name
+ *
+ * @property (?RedundancyGroupState)|Query $state
+ * @property Dependency|Query $dependency
+ */
+class RedundancyGroup extends Model
+{
+    public function getTableName(): string
+    {
+        return 'redundancy_group';
+    }
+
+    public function getKeyName(): string
+    {
+        return 'id';
+    }
+
+    public function getColumns(): array
+    {
+        return [
+            'name',
+            'display_name'
+        ];
+    }
+
+    public function createBehaviors(Behaviors $behaviors): void
+    {
+        $behaviors->add(new Binary([
+            'id'
+        ]));
+        $behaviors->add(new ReRoute([
+            'child' => 'dependency_node.child',
+            'parent' => 'dependency_node.parent'
+        ]));
+    }
+
+    public function createRelations(Relations $relations): void
+    {
+        $relations->belongsTo('dependency_node', DependencyNode::class)
+            ->setForeignKey('redundancy_group_id')
+            ->setCandidateKey('id');
+
+        $relations->hasOne('state', RedundancyGroupState::class)
+            ->setJoinType('LEFT');
+
+        $relations->hasMany('dependency', Dependency::class);
+    }
+}
diff --git a/library/Icingadb/Model/RedundancyGroupState.php b/library/Icingadb/Model/RedundancyGroupState.php
new file mode 100644
index 000000000..1d8da858f
--- /dev/null
+++ b/library/Icingadb/Model/RedundancyGroupState.php
@@ -0,0 +1,58 @@
+<?php
+
+/* Icinga DB Web | (c) 2024 Icinga GmbH | GPLv2 */
+
+namespace Icinga\Module\Icingadb\Model;
+
+use ipl\Orm\Behavior\Binary;
+use ipl\Orm\Behavior\BoolCast;
+use ipl\Orm\Behaviors;
+use ipl\Orm\Model;
+use ipl\Orm\Query;
+use ipl\Orm\Relations;
+
+/**
+ * Redundancy group state model.
+ *
+ * @property string $id
+ * @property string $redundancy_group_id
+ * @property bool $failed
+ *
+ * @property RedundancyGroup|Query $redundancy_group
+ */
+class RedundancyGroupState extends Model
+{
+    public function getTableName(): string
+    {
+        return 'redundancy_group_state';
+    }
+
+    public function getKeyName(): string
+    {
+        return 'id';
+    }
+
+    public function getColumns(): array
+    {
+        return [
+            'redundancy_group_id',
+            'failed'
+        ];
+    }
+
+    public function createBehaviors(Behaviors $behaviors): void
+    {
+        $behaviors->add(new Binary([
+            'id',
+            'redundancy_group_id'
+        ]));
+        $behaviors->add(new BoolCast([
+            'failed'
+        ]));
+    }
+
+    public function createRelations(Relations $relations): void
+    {
+        $relations->belongsTo('redundancy_group', RedundancyGroup::class);
+    }
+}
diff --git a/library/Icingadb/Model/Service.php b/library/Icingadb/Model/Service.php
index 1d97b96ac..1383823ab 100644
--- a/library/Icingadb/Model/Service.php
+++ b/library/Icingadb/Model/Service.php
@@ -170,6 +170,8 @@ public function createBehaviors(Behaviors $behaviors)
         ]));
 
         $behaviors->add(new ReRoute([
+            'child'         => 'dependency_node.child',
+            'parent'        => 'dependency_node.parent',
             'user'          => 'notification.user',
             'usergroup'     => 'notification.usergroup'
         ]));
@@ -222,6 +224,8 @@ public function createDefaults(Defaults $defaults)
 
     public function createRelations(Relations $relations)
     {
+        $relations->belongsTo('dependency_node', DependencyNode::class)
+            ->setJoinType('LEFT');
         $relations->belongsTo('environment', Environment::class);
         $relations->belongsTo('host', Host::class)->setJoinType('LEFT');
         $relations->belongsTo('checkcommand', Checkcommand::class);
diff --git a/library/Icingadb/Model/Timeperiod.php b/library/Icingadb/Model/Timeperiod.php
index e1664103b..34ff55096 100644
--- a/library/Icingadb/Model/Timeperiod.php
+++ b/library/Icingadb/Model/Timeperiod.php
@@ -98,5 +98,6 @@ public function createRelations(Relations $relations)
         $relations->hasMany('service', Service::class)
             ->setForeignKey('check_timeperiod_id');
         $relations->hasMany('user', User::class);
+        $relations->hasMany('dependency', Dependency::class);
     }
 }
diff --git a/library/Icingadb/Model/UnreachableParent.php b/library/Icingadb/Model/UnreachableParent.php
new file mode 100644
index 000000000..de3608a3c
--- /dev/null
+++ b/library/Icingadb/Model/UnreachableParent.php
@@ -0,0 +1,181 @@
+<?php
+
+/* Icinga DB Web | (c) 2024 Icinga GmbH | GPLv2 */
+
+namespace Icinga\Module\Icingadb\Model;
+
+use Icinga\Module\Icingadb\Model\Behavior\ReRoute;
+use InvalidArgumentException;
+use ipl\Orm\Behavior\Binary;
+use ipl\Orm\Behaviors;
+use ipl\Orm\Model;
+use ipl\Orm\Query;
+use ipl\Orm\Relations;
+use ipl\Sql\Connection;
+use ipl\Sql\Expression;
+use ipl\Sql\Select;
+use ipl\Stdlib\Filter;
+
+/**
+ * Class UnreachableParent
+ *
+ * @property string $id
+ * @property int $level
+ * @property ?string $host_id
+ * @property ?string $service_id
+ * @property ?string $redundancy_group_id
+ * @property ?string $dependency_id
+ * @property int $is_group_member
+ *
+ * @property (?Host)|Query $host
+ * @property (?Service)|Query $service
+ * @property (?RedundancyGroup)|Query $redundancy_group
+ * @property (?Dependency)|Query $dependency
+ */
+class UnreachableParent extends Model
+{
+    public function getTableName(): string
+    {
+        return 'unreachable_parent';
+    }
+
+    public function getKeyName(): string
+    {
+        return 'id';
+    }
+
+    public function getColumns(): array
+    {
+        return [
+            'id',
+            'level',
+            'host_id',
+            'service_id',
+            'redundancy_group_id',
+            'dependency_id',
+            'is_group_member'
+        ];
+    }
+
+    public function createRelations(Relations $relations): void
+    {
+        $relations->belongsTo('host', Host::class)
+            ->setJoinType('LEFT');
+        $relations->belongsTo('service', Service::class)
+            ->setJoinType('LEFT');
+        $relations->belongsTo('redundancy_group', RedundancyGroup::class)
+            ->setJoinType('LEFT');
+        $relations->belongsTo('dependency', Dependency::class)
+            ->setJoinType('LEFT');
+    }
+
+    public function createBehaviors(Behaviors $behaviors): void
+    {
+        $behaviors->add(new Binary([
+            'id',
+            'host_id',
+            'service_id',
+            'redundancy_group_id',
+            'dependency_id'
+        ]));
+
+        $behaviors->add(new ReRoute([
+            'hostgroup'     => 'host.hostgroup',
+            'servicegroup'  => 'service.servicegroup'
+        ]));
+    }
+
+    public static function on(Connection $db, Model $root = null): Query
+    {
+        if ($root === null) {
+            throw new InvalidArgumentException('Root node must not be null');
+        }
+
+        $query = parent::on($db);
+        $query->getSelectBase()->with(
+            self::selectNodes($db, $root),
+            'unreachable_parent',
+            true
+        )->where([
+            'unreachable_parent.level > ?' => 0,
+            'unreachable_parent.is_group_member = ?' => 0
+        ]);
+
+        return $query;
+    }
+
+    private static function selectNodes(Connection $db, Model $root): Select
+    {
+        $rootQuery = DependencyNode::on($db)
+            ->columns([
+                'id' => 'id',
+                'level' => new Expression('0'),
+                'host_id' => 'host_id',
+                'service_id' => new Expression("COALESCE(%s, CAST('' as binary(20)))", ['service_id']),
+                'redundancy_group_id' => new Expression("CAST('' as binary(20))"),
+                'dependency_id' => new Expression("CAST('' as binary(20))"),
+                'is_group_member' => new Expression('0')
+            ]);
+        if ($root instanceof Host) {
+            $rootQuery->filter(Filter::all(
+                Filter::equal('host_id', $root->id),
+                Filter::unlike('service_id', '*')
+            ));
+        } elseif ($root instanceof Service) {
+            $rootQuery->filter(Filter::all(
+                Filter::equal('host_id', $root->host_id),
+                Filter::equal('service_id', $root->id)
+            ));
+        } else {
+            throw new InvalidArgumentException('Root node must be either a host or a service');
+        }
+
+        $nodeQuery = DependencyEdge::on($db)
+            ->columns([
+                'id' => 'to_node_id',
+                'level' => new Expression('urn.level + 1'),
+                'host_id' => 'to.host_id',
+                'service_id' => 'to.service_id',
+                'redundancy_group_id' => 'to.redundancy_group_id',
+                'dependency_id' => 'dependency_id',
+                'is_group_member' => new Expression('urn.redundancy_group_id IS NOT NULL AND urn.level > 0')
+            ]);
+        $nodeQuery->filter(Filter::any(
+            Filter::equal('dependency.state.failed', 'y'),
+            Filter::equal('to.redundancy_group.state.failed', 'y')
+        ));
+
+        $nodeSelect = $nodeQuery->assembleSelect();
+
+        // TODO: ipl-orm doesn't preserve key order :'(
+        $columnsProperty = (new \ReflectionClass($nodeSelect))->getProperty('columns');
+        $columnsProperty->setAccessible(true);
+        $columnsProperty->setValue($nodeSelect, array_merge(
+            [
+                'id' => null,
+                'level' => null,
+                'host_id' => null,
+                'service_id' => null,
+                'redundancy_group_id' => null,
+                'dependency_id' => null,
+                'is_group_member' => null
+            ],
+            $nodeSelect->getColumns()
+        ));
+
+        return $rootQuery->assembleSelect()->union(
+            $nodeSelect
+                ->join(['urn' => 'unreachable_parent'], sprintf(
+                    'urn.id = %s',
+                    $nodeQuery
+                        ->getResolver()
+                        ->qualifyColumn(
+                            'from_node_id',
+                            $nodeQuery
+                                ->getResolver()
+                                ->getAlias($nodeQuery->getModel())
+                        )
+                ))
+        );
+    }
+}