diff --git a/nomad/structs/network.go b/nomad/structs/network.go
index 33327a50b8a..1cbcce85572 100644
--- a/nomad/structs/network.go
+++ b/nomad/structs/network.go
@@ -95,11 +95,14 @@ func (idx *NetworkIndex) AddReserved(n *NetworkResource) (collide bool) {
 		used = make(map[int]struct{})
 		idx.UsedPorts[n.IP] = used
 	}
-	for _, port := range n.ReservedPorts {
-		if _, ok := used[port.Value]; ok {
-			collide = true
-		} else {
-			used[port.Value] = struct{}{}
+
+	for _, ports := range [][]Port{n.ReservedPorts, n.DynamicPorts} {
+		for _, port := range ports {
+			if _, ok := used[port.Value]; ok {
+				collide = true
+			} else {
+				used[port.Value] = struct{}{}
+			}
 		}
 	}
 
@@ -179,8 +182,11 @@ func (idx *NetworkIndex) AssignNetwork(ask *NetworkResource) (out *NetworkResour
 			if _, ok := idx.UsedPorts[ipStr][randPort]; ok {
 				goto PICK
 			}
-			if isPortReserved(offer.ReservedPorts, randPort) {
-				goto PICK
+
+			for _, ports := range [][]Port{offer.ReservedPorts, offer.DynamicPorts} {
+				if isPortReserved(ports, randPort) {
+					goto PICK
+				}
 			}
 			offer.DynamicPorts[i].Value = randPort
 		}
diff --git a/nomad/structs/structs.go b/nomad/structs/structs.go
index d1c5c666d44..df7aa5f9ddd 100644
--- a/nomad/structs/structs.go
+++ b/nomad/structs/structs.go
@@ -645,6 +645,10 @@ func (n *NetworkResource) Copy() *NetworkResource {
 		newR.ReservedPorts = make([]Port, len(n.ReservedPorts))
 		copy(newR.ReservedPorts, n.ReservedPorts)
 	}
+	if n.DynamicPorts != nil {
+		newR.DynamicPorts = make([]Port, len(n.DynamicPorts))
+		copy(newR.DynamicPorts, n.DynamicPorts)
+	}
 	return newR
 }
 
diff --git a/scheduler/generic_sched_test.go b/scheduler/generic_sched_test.go
index e3e87557804..33abef8a498 100644
--- a/scheduler/generic_sched_test.go
+++ b/scheduler/generic_sched_test.go
@@ -60,6 +60,19 @@ func TestServiceSched_JobRegister(t *testing.T) {
 		t.Fatalf("bad: %#v", out)
 	}
 
+	// Ensure different ports were used.
+	used := make(map[int]struct{})
+	for _, alloc := range out {
+		for _, resource := range alloc.TaskResources {
+			for _, port := range resource.Networks[0].DynamicPorts {
+				if _, ok := used[port.Value]; ok {
+					t.Fatalf("Port collision %v", port.Value)
+				}
+				used[port.Value] = struct{}{}
+			}
+		}
+	}
+
 	h.AssertEvalStatus(t, structs.EvalStatusComplete)
 }