diff --git a/ddsrouter_core/test/blackbox/ddsrouter_core/dds/WAN/DDSTestWAN.cpp b/ddsrouter_core/test/blackbox/ddsrouter_core/dds/WAN/DDSTestWAN.cpp
index 26584f1f1..c5b1461ab 100644
--- a/ddsrouter_core/test/blackbox/ddsrouter_core/dds/WAN/DDSTestWAN.cpp
+++ b/ddsrouter_core/test/blackbox/ddsrouter_core/dds/WAN/DDSTestWAN.cpp
@@ -128,6 +128,13 @@ discovery_server_participant_configuration(
             );
     }
 
+    // Localhost translation is never accomplished in DS with Fast DDS 2.x due to fixed GUIDs.
+    // TCPv6 suffers from this issue as it will not be able to make any connection. A whitelist is needed to enforce
+    // localhost connections.
+    // This issue is fixed in Fast DDS 3.x with machine_id based translations and non-fixed GUIDs DS's.
+    participants::types::WhitelistType lo_wl = (ip_version == participants::types::IpVersion::v4 ? "127.0.0.1" : "::1");
+    conf.whitelist.insert(lo_wl);
+
     conf.id = core::types::ParticipantId("WanDsParticipant_" + std::to_string((this_server_id_is_1 ? 1 : 0)));
 
     conf.discovery_server_guid_prefix = core::types::GuidPrefix((this_server_id_is_1 ? 1u : 0u));
diff --git a/ddsrouter_core/test/blackbox/ddsrouter_core/dds/types/test_participants.hpp b/ddsrouter_core/test/blackbox/ddsrouter_core/dds/types/test_participants.hpp
index 940880203..1b5a6f531 100644
--- a/ddsrouter_core/test/blackbox/ddsrouter_core/dds/types/test_participants.hpp
+++ b/ddsrouter_core/test/blackbox/ddsrouter_core/dds/types/test_participants.hpp
@@ -286,10 +286,6 @@ class TestSubscriber
     {
         if (participant_ != nullptr)
         {
-            if (topic_ != nullptr)
-            {
-                participant_->delete_topic(topic_);
-            }
             if (subscriber_ != nullptr)
             {
                 if (reader_ != nullptr)
@@ -298,6 +294,10 @@ class TestSubscriber
                 }
                 participant_->delete_subscriber(subscriber_);
             }
+            if (topic_ != nullptr)
+            {
+                participant_->delete_topic(topic_);
+            }
             eprosima::fastdds::dds::DomainParticipantFactory::get_instance()->delete_participant(participant_);
         }
     }