diff --git a/tempest/common/fixed_network.py b/tempest/common/fixed_network.py
index b06ddf2..b533898 100644
--- a/tempest/common/fixed_network.py
+++ b/tempest/common/fixed_network.py
@@ -15,6 +15,7 @@
 
 from tempest_lib import exceptions as lib_exc
 
+from tempest.common import isolated_creds
 from tempest import config
 from tempest import exceptions
 
@@ -38,7 +39,7 @@
     network = None
     # NOTE(andreaf) get_primary_network will always be available once
     # bp test-accounts-continued is implemented
-    if (CONF.auth.allow_tenant_isolation and
+    if (isinstance(creds_provider, isolated_creds.IsolatedCreds) and
         (CONF.service_available.neutron and
          not CONF.service_available.ironic)):
         network = creds_provider.get_primary_network()
diff --git a/tempest/test.py b/tempest/test.py
index da936b4..2585999 100644
--- a/tempest/test.py
+++ b/tempest/test.py
@@ -445,7 +445,12 @@
         # Make sure isolated_creds exists and get a network client
         networks_client = cls.get_client_manager().networks_client
         isolated_creds = getattr(cls, 'isolated_creds', None)
-        if credentials.is_admin_available():
+        # In case of nova network, isolated tenants are not able to list the
+        # network configured in fixed_network_name, even if the can use it
+        # for their servers, so using an admin network client to validate
+        # the network name
+        if (not CONF.service_available.neutron and
+                credentials.is_admin_available()):
             admin_creds = isolated_creds.get_admin_creds()
             networks_client = clients.Manager(admin_creds).networks_client
         return fixed_network.get_tenant_network(isolated_creds,