diff --git a/.gitignore b/.gitignore
index 7cf28aed43..4e7c9b7103 100644
--- a/.gitignore
+++ b/.gitignore
@@ -201,7 +201,13 @@ $RECYCLE.BIN/
 # Windows shortcuts
 *.lnk
 
-# End of https://www.gitignore.io/api/java,macos,windows,eclipse
+# Metals
+.metals/
+.bloop/
+project/**/metals.sbt
+
+
+# End of https://www.gitignore.io/api/java,macos,windows,eclipse, metals
 
 /target/
 
diff --git a/src/main/scala/edu/ie3/simona/model/grid/GridModel.scala b/src/main/scala/edu/ie3/simona/model/grid/GridModel.scala
index f2eab5ff1d..af90cfc344 100644
--- a/src/main/scala/edu/ie3/simona/model/grid/GridModel.scala
+++ b/src/main/scala/edu/ie3/simona/model/grid/GridModel.scala
@@ -29,7 +29,6 @@ import org.jgrapht.graph.{DefaultEdge, SimpleGraph}
 
 import java.time.ZonedDateTime
 import java.util.UUID
-import scala.collection.immutable.ListSet
 import scala.jdk.CollectionConverters._
 
 /** Representation of one physical electrical grid. It holds the references to
@@ -440,19 +439,6 @@ object GridModel {
       throw new InvalidGridException(
         s"The grid model for subnet ${gridModel.subnetNo} has multiple nodes with the same name!"
       )
-
-    // multiple switches @ one node -> not supported yet!
-    val switchVector = gridModel.gridComponents.switches.foldLeft(
-      Vector.empty[UUID]
-    )((vector, switch) => (vector :+ switch.nodeAUuid) :+ switch.nodeBUuid)
-    val uniqueSwitchNodeIds = switchVector.toSet.toList
-    if (switchVector.diff(uniqueSwitchNodeIds).nonEmpty) {
-      throw new InvalidGridException(
-        s"The grid model for subnet ${gridModel.subnetNo} has nodes with multiple switches. This is not supported yet! Duplicates are located @ nodes: ${switchVector
-            .diff(uniqueSwitchNodeIds)}"
-      )
-    }
-
   }
 
   /** Checks all ControlGroups if a) Transformer of ControlGroup and Measurement
@@ -646,40 +632,82 @@ object GridModel {
   def updateUuidToIndexMap(gridModel: GridModel): Unit = {
 
     val switches = gridModel.gridComponents.switches
-    val nodes = gridModel.gridComponents.nodes
+    val nodes = gridModel.gridComponents.nodes.distinct
+
+    // map for each node that is directly connected to a switch,
+    // to all nodes that are directly connected via switch
+    val nodeConnections: Map[UUID, Set[UUID]] =
+      switches.filter(_.isClosed).foldLeft(Map.empty[UUID, Set[UUID]]) {
+        (acc, switch) =>
+          acc
+            .updated(
+              switch.nodeAUuid,
+              acc.getOrElse(switch.nodeAUuid, Set.empty) + switch.nodeBUuid,
+            )
+            .updated(
+              switch.nodeBUuid,
+              acc.getOrElse(switch.nodeBUuid, Set.empty) + switch.nodeAUuid,
+            )
+      }
 
-    val nodesAndSwitches: ListSet[SystemComponent] = ListSet
-      .empty[SystemComponent] ++ switches ++ nodes
+    // create sets of nodes to be fused together and assign common indices
+    val switchConnectedNodes =
+      findConnectedNodes(nodeConnections).zipWithIndex.flatMap {
+        case (nodes, idx) => nodes.map(_ -> idx)
+      }.toMap
 
-    val updatedNodeToUuidMap = nodesAndSwitches
+    // also account for all missing nodes (not connected to a switch)
+    val offset = switchConnectedNodes.values.maxOption.map(_ + 1).getOrElse(0)
+    val (updatedNodeToUuidMap, _) = nodes
       .filter(_.isInOperation)
-      .filter {
-        case switch: SwitchModel => switch.isClosed
-        case _: NodeModel        => true
-      }
-      .zipWithIndex
-      .foldLeft(Map.empty[UUID, Int]) {
-        case (map, (gridComponent, componentId)) =>
-          gridComponent match {
-            case switchModel: SwitchModel =>
-              map ++ Map(
-                switchModel.nodeAUuid -> componentId,
-                switchModel.nodeBUuid -> componentId,
-              )
-
-            case nodeModel: NodeModel =>
-              if (!map.contains(nodeModel.uuid)) {
-                val idx = map.values.toList.sorted.lastOption
-                  .getOrElse(
-                    -1
-                  ) + 1 // if we didn't found anything in the list, we don't have switches and want to start @ 0
-                map + (nodeModel.uuid -> idx)
-              } else {
-                map
-              }
+      .foldLeft(Map.empty[UUID, Int], offset) {
+        case ((map, nextIdx), nodeModel) =>
+          switchConnectedNodes.get(nodeModel.uuid) match {
+            case Some(idx) => (map + (nodeModel.uuid -> idx), nextIdx)
+            case None =>
+              (map + (nodeModel.uuid -> nextIdx), nextIdx + 1)
           }
       }
 
     gridModel._nodeUuidToIndexMap = updatedNodeToUuidMap
   }
+
+  /** Build sets of connected nodes via depth-first search
+    *
+    * @param nodeConnections
+    *   The connected nodes for each node
+    * @return
+    *   The sets of nodes
+    */
+  private def findConnectedNodes(
+      nodeConnections: Map[UUID, Set[UUID]]
+  ): Seq[Seq[UUID]] = {
+
+    def dfs(node: UUID, visited: Set[UUID] = Set.empty): Set[UUID] = {
+      nodeConnections
+        .getOrElse(node, Set.empty)
+        .foldLeft(visited + node) { case (accVisited, neighbor) =>
+          if (accVisited.contains(neighbor))
+            accVisited
+          else
+            dfs(neighbor, accVisited)
+        }
+    }
+
+    val (_, components) =
+      nodeConnections.keys.foldLeft((Set.empty[UUID], Seq.empty[Seq[UUID]])) {
+        case ((visited, components), node) =>
+          if (visited.contains(node)) {
+            (visited, components)
+          } else {
+            val component = dfs(node)
+            val updatedVisited = visited ++ component
+            val updatedComponents = components :+ component.toSeq
+
+            (updatedVisited, updatedComponents)
+          }
+      }
+
+    components
+  }
 }
diff --git a/src/test/scala/edu/ie3/simona/model/grid/GridSpec.scala b/src/test/scala/edu/ie3/simona/model/grid/GridSpec.scala
index dc4fab6ef2..2f29248054 100644
--- a/src/test/scala/edu/ie3/simona/model/grid/GridSpec.scala
+++ b/src/test/scala/edu/ie3/simona/model/grid/GridSpec.scala
@@ -9,12 +9,14 @@ package edu.ie3.simona.model.grid
 import breeze.linalg.DenseMatrix
 import breeze.math.Complex
 import breeze.numerics.abs
-import edu.ie3.datamodel.exceptions.InvalidGridException
 import edu.ie3.datamodel.models.input.MeasurementUnitInput
 import edu.ie3.datamodel.models.voltagelevels.GermanVoltageLevelUtils
 import edu.ie3.simona.exceptions.GridInconsistencyException
 import edu.ie3.simona.model.control.{GridControls, TransformerControlGroupModel}
-import edu.ie3.simona.model.grid.GridModel.GridComponents
+import edu.ie3.simona.model.grid.GridModel.{
+  GridComponents,
+  updateUuidToIndexMap,
+}
 import edu.ie3.simona.test.common.input.{GridInputTestData, LineInputTestData}
 import edu.ie3.simona.test.common.model.grid.{
   BasicGrid,
@@ -265,53 +267,6 @@ class GridSpec
 
     }
 
-    "throw an InvalidGridException if two switches are connected @ the same node" in new BasicGridWithSwitches {
-      // enable nodes
-      override val nodes: Seq[NodeModel] = super.nodes
-      nodes.foreach(_.enable())
-
-      // add a second switch @ node13 (between node1 and node13)
-      val secondSwitch = new SwitchModel(
-        UUID.fromString("ebeaad04-0ee3-4b2e-ae85-8c76a583295b"),
-        "SecondSwitch1",
-        defaultOperationInterval,
-        node1.uuid,
-        node13.uuid,
-      )
-      // add the second switch + enable switches
-      override val switches: Set[SwitchModel] = super.switches + secondSwitch
-      switches.foreach(_.enable())
-      // open the switches
-      switches.foreach(_.open())
-
-      // get the grid from the raw data
-      val gridModel = new GridModel(
-        1,
-        default400Kva10KvRefSystem,
-        GridComponents(
-          nodes,
-          lines,
-          Set(transformer2wModel),
-          Set.empty[Transformer3wModel],
-          switches,
-        ),
-        GridControls.empty,
-      )
-
-      // get the private method for validation
-      val validateConsistency: PrivateMethod[Unit] =
-        PrivateMethod[Unit](Symbol("validateConsistency"))
-
-      // call the validation method
-      val exception: InvalidGridException = intercept[InvalidGridException] {
-        GridModel invokePrivate validateConsistency(gridModel)
-      }
-
-      // expect an exception for node 13
-      exception.getMessage shouldBe s"The grid model for subnet 1 has nodes with multiple switches. This is not supported yet! Duplicates are located @ nodes: Vector(${node13.uuid})"
-
-    }
-
     "update the nodeUuidToIndexMap correctly, when the given grid" must {
 
       "contain 3 open switches" in new BasicGridWithSwitches {
@@ -474,6 +429,131 @@ class GridSpec
           nodes.map(node => node.uuid).toVector.sorted
         )
       }
+
+      "contains two closed switches with a common node" in new BasicGridWithSwitches {
+        // enable nodes
+        override val nodes: Seq[NodeModel] = super.nodes
+        nodes.foreach(_.enable())
+
+        // add a second switch @ node13 (between node1 and node13)
+        val secondSwitch = new SwitchModel(
+          UUID.fromString("ebeaad04-0ee3-4b2e-ae85-8c76a583295b"),
+          "SecondSwitch1",
+          defaultOperationInterval,
+          node1.uuid,
+          node13.uuid,
+        )
+        // add the second switch + enable switches
+        override val switches: Set[SwitchModel] = super.switches + secondSwitch
+        switches.foreach(_.enable())
+        // close the switches
+        switches.foreach(_.close())
+
+        // get the grid from the raw data
+        val gridModel = new GridModel(
+          1,
+          default400Kva10KvRefSystem,
+          GridComponents(
+            nodes,
+            lines,
+            Set(transformer2wModel),
+            Set.empty[Transformer3wModel],
+            switches,
+          ),
+          GridControls.empty,
+        )
+
+        updateUuidToIndexMap(gridModel)
+
+        // nodes 1, 13 and 14 should map to the same node
+        val node1Index = gridModel.nodeUuidToIndexMap
+          .get(node1.uuid)
+          .value
+        gridModel.nodeUuidToIndexMap.get(node13.uuid).value shouldBe node1Index
+        gridModel.nodeUuidToIndexMap.get(node14.uuid).value shouldBe node1Index
+      }
+
+      "contains closed switches in a complex pattern" in new BasicGridWithSwitches {
+        // just six nodes from the basic grid
+        override val nodes: Seq[NodeModel] =
+          Seq(node1, node2, node3, node4, node5, node6)
+        nodes.foreach(_.enable())
+
+        // nodes 1-4 connected by switches in a rectangle plus diagonal,
+        // nodes 5-6 connected separately
+        override val switches: Set[SwitchModel] = Set(
+          SwitchModel(
+            UUID.fromString("0-0-0-0-1"),
+            "Switch1",
+            defaultOperationInterval,
+            node1.uuid,
+            node2.uuid,
+          ),
+          SwitchModel(
+            UUID.fromString("0-0-0-0-2"),
+            "Switch2",
+            defaultOperationInterval,
+            node2.uuid,
+            node3.uuid,
+          ),
+          SwitchModel(
+            UUID.fromString("0-0-0-0-3"),
+            "Switch3",
+            defaultOperationInterval,
+            node3.uuid,
+            node4.uuid,
+          ),
+          SwitchModel(
+            UUID.fromString("0-0-0-0-4"),
+            "Switch4",
+            defaultOperationInterval,
+            node1.uuid,
+            node4.uuid,
+          ),
+          SwitchModel(
+            UUID.fromString("0-0-0-0-5"),
+            "Switch5",
+            defaultOperationInterval,
+            node2.uuid,
+            node4.uuid,
+          ),
+          SwitchModel(
+            UUID.fromString("0-0-0-0-6"),
+            "Switch6",
+            defaultOperationInterval,
+            node5.uuid,
+            node6.uuid,
+          ),
+        )
+        switches.foreach(_.enable())
+        // close the switches
+        switches.foreach(_.close())
+
+        // get the grid from the raw data
+        val gridModel = new GridModel(
+          1,
+          default400Kva10KvRefSystem,
+          GridComponents(
+            nodes,
+            Set.empty,
+            Set.empty,
+            Set.empty,
+            switches,
+          ),
+          GridControls.empty,
+        )
+
+        // testing the assignment of nodes to indices
+        updateUuidToIndexMap(gridModel)
+
+        gridModel.nodeUuidToIndexMap.get(node1.uuid).value shouldBe 0
+        gridModel.nodeUuidToIndexMap.get(node2.uuid).value shouldBe 0
+        gridModel.nodeUuidToIndexMap.get(node3.uuid).value shouldBe 0
+        gridModel.nodeUuidToIndexMap.get(node4.uuid).value shouldBe 0
+        gridModel.nodeUuidToIndexMap.get(node5.uuid).value shouldBe 1
+        gridModel.nodeUuidToIndexMap.get(node6.uuid).value shouldBe 1
+      }
+
     }
 
     "build correct transformer control models" should {