diff --git a/ansible/kolla-bifrost-hostvars.yml b/ansible/kolla-bifrost-hostvars.yml
index 0de2d8010..3926f8f93 100644
--- a/ansible/kolla-bifrost-hostvars.yml
+++ b/ansible/kolla-bifrost-hostvars.yml
@@ -17,7 +17,7 @@
       deploy_image_filename: "{{ kolla_bifrost_deploy_image_filename }}"
       ipv4_interface_mac: "{% raw %}{{ extra.pxe_interface_mac | default }}{% endraw %}"
       ipv4_address: "{{ admin_oc_net_name | net_ip }}"
-      ipv4_subnet_mask: "{{ admin_oc_net_name | net_cidr | ipaddr('netmask') }}"
+      ipv4_subnet_mask: "{{ admin_oc_net_name | net_mask }}"
       # If the admin network does not have a gateway defined, use the
       # seed as a gateway to allow external access until other networks have
       # been configured.