diff --git a/client/src/main/scala/tmt/views/SubscriptionView.scala b/client/src/main/scala/tmt/views/SubscriptionView.scala
index fbcd4e2..9126ae7 100644
--- a/client/src/main/scala/tmt/views/SubscriptionView.scala
+++ b/client/src/main/scala/tmt/views/SubscriptionView.scala
@@ -5,7 +5,7 @@ import rx._
 import tmt.framework.Framework._
 import tmt.framework.Helpers._
 import tmt.shared.models.{Connection, ConnectionSet, RoleMappings}
-
+import monifu.concurrent.Implicits.globalScheduler
 import scalatags.JsDom.all._
 
 class SubscriptionView(roleMappings: RoleMappings, connectionSet: ConnectionSet) {
@@ -50,8 +50,9 @@ class SubscriptionView(roleMappings: RoleMappings, connectionSet: ConnectionSet)
   }
 
   def addConnection() = {
-    subscribe(connection())
-    connections() = connections() + connection()
+    subscribe(connection()).onSuccess {
+      case _ => connections() = connections() + connection()
+    }
   }
 
   def removeConnection(connection: Connection) = {
diff --git a/common/src/main/scala/tmt/library/Role.scala b/common/src/main/scala/tmt/library/Role.scala
index 379fe4e..db8c5e0 100644
--- a/common/src/main/scala/tmt/library/Role.scala
+++ b/common/src/main/scala/tmt/library/Role.scala
@@ -2,7 +2,7 @@ package tmt.library
 
 import enumeratum.{Enum, EnumEntry}
 
-sealed abstract class Role(maybeConsumes: Option[ItemType], maybeProduces: Option[ItemType]) extends EnumEntry
+sealed abstract class Role(val maybeConsumes: Option[ItemType], val maybeProduces: Option[ItemType]) extends EnumEntry
 sealed abstract class SourceRole(override val entryName: String, val produces: ItemType) extends Role(None, Some(produces))
 sealed abstract class SinkRole(override val entryName: String, val consumes: ItemType) extends Role(Some(consumes), None)
 sealed abstract class FlowRole(override val entryName: String, val consumes: ItemType, val produces: ItemType) extends Role(Some(consumes), Some(produces))
diff --git a/frontend/app/controllers/StreamController.scala b/frontend/app/controllers/StreamController.scala
index bcf4808..df34866 100644
--- a/frontend/app/controllers/StreamController.scala
+++ b/frontend/app/controllers/StreamController.scala
@@ -4,7 +4,7 @@ import javax.inject.{Inject, Singleton}
 
 import common.AppSettings
 import play.api.mvc.{Action, Controller}
-import services.{ClusterClientService, ConnectionSetService, RoleMappingsService}
+import services.{ValidationFailedException, ClusterClientService, ConnectionSetService, RoleMappingsService}
 import templates.Page
 import upickle.default._
 
@@ -46,7 +46,10 @@ class StreamController @Inject()(
 
   def subscribe(serverName: String, topic: String) = Action {
     clusterClientService.subscribe(serverName, topic)
-    Accepted("ok")
+      .map(_ => Accepted("ok"))
+      .recover {
+      case ValidationFailedException(msg) => BadGateway(msg)
+    }.get
   }
 
   def unsubscribe(serverName: String, topic: String) = Action {
diff --git a/frontend/app/services/ClusterClientService.scala b/frontend/app/services/ClusterClientService.scala
index 68f46ee..3113d3a 100644
--- a/frontend/app/services/ClusterClientService.scala
+++ b/frontend/app/services/ClusterClientService.scala
@@ -9,13 +9,15 @@ import akka.cluster.pubsub.DistributedPubSubMediator.Publish
 import akka.pattern.ask
 import akka.util.Timeout
 import tmt.common.Messages
+import tmt.library.Role
 import tmt.shared.Topics
 import tmt.shared.models.ConnectionSet
 
 import scala.concurrent.duration.{DurationInt, FiniteDuration}
+import scala.util.{Failure, Success, Try}
 
 @Singleton
-class ClusterClientService @Inject()(system: ActorSystem) {
+class ClusterClientService @Inject()(system: ActorSystem, roleMappingsService: RoleMappingsService) {
 
   implicit val timeout = Timeout(2.seconds)
 
@@ -26,8 +28,13 @@ class ClusterClientService @Inject()(system: ActorSystem) {
     mediator ! Publish(Topics.Throttle, Messages.UpdateDelay(serverName, delay))
   }
 
-  def subscribe(serverName: String, topic: String) = {
-    mediator ! Publish(Topics.Subscription, Messages.Subscribe(serverName, topic))
+  def subscribe(serverName: String, topic: String): Try[Unit] = {
+    validate(serverName, topic) match {
+      case Some(true) =>
+        Success(mediator ! Publish(Topics.Subscription, Messages.Subscribe(serverName, topic)))
+      case _          =>
+        Failure(new ValidationFailedException("Bad request"))
+    }
   }
 
   def unsubscribe(serverName: String, topic: String) = {
@@ -35,4 +42,17 @@ class ClusterClientService @Inject()(system: ActorSystem) {
   }
 
   def allConnections = (connectionStore ? ConnectionStore.GetConnections).mapTo[ConnectionSet]
+
+  private def validate(sourceServerName: String, destinationServerName: String) = {
+    val roleMappings = roleMappingsService.onlineRoleMappings
+
+    for {
+      sourceRoleName <- roleMappings.roleOf(sourceServerName)
+      destinationRoleName <- roleMappings.roleOf(destinationServerName)
+      sourceRole = Role.withName(sourceRoleName)
+      destinationRole = Role.withName(destinationRoleName)
+    } yield sourceRole.maybeConsumes.isDefined && sourceRole.maybeConsumes == destinationRole.maybeProduces
+  }
 }
+
+case class ValidationFailedException(msg: String) extends RuntimeException(msg)
diff --git a/shared/src/main/scala/tmt/shared/models/RoleMappings.scala b/shared/src/main/scala/tmt/shared/models/RoleMappings.scala
index 684eef6..e79f40d 100644
--- a/shared/src/main/scala/tmt/shared/models/RoleMappings.scala
+++ b/shared/src/main/scala/tmt/shared/models/RoleMappings.scala
@@ -8,4 +8,10 @@ case class RoleMappings(mappings: Map[String, Seq[String]]) {
       role -> serverNames.filter(onlineRoles)
     }
   }
+  def roleOf(serverName: String) = {
+    mappings.find { mapping =>
+      val servers = mapping._2
+      servers.contains(serverName)
+    }.map(_._1)
+  }
 }