diff --git a/k8s/rally-files/openstack-mos-scn-i100-static-users.json b/k8s/rally-files/openstack-mos-scn-i100-static-users.json
index b4f1c75..0eecdbc 100644
--- a/k8s/rally-files/openstack-mos-scn-i100-static-users.json
+++ b/k8s/rally-files/openstack-mos-scn-i100-static-users.json
@@ -2,7 +2,7 @@
 {% set image_name = image_name or "cvp.cirros.51" %}
 {% set availability_zone = "nova" %}
 {% set concurrency = 10 %}
-{% set volume_size =  %}
+{% set volume_size = 1 %}
 {% set times = 100 %}
 {% set users = 5 %}
 {% set tenants = 4 %}
diff --git a/scripts/prepare.sh b/scripts/prepare.sh
index c0b58ba..9e3e78f 100644
--- a/scripts/prepare.sh
+++ b/scripts/prepare.sh
@@ -293,8 +293,8 @@
     echo router add subnet ${router_id} ${subnet2_id} >>${cmds}
     process_cmds
 
-    # TODO: Search for external net
-    external=prod-public
+    # get external network name
+    external=$(openstack network list --external -c Name -f value | head -n1)
     echo router set ${router} --external-gateway ${external} >>${cmds}
     process_cmds
 }