diff --git a/network/service_net_map.j2.yaml b/network/service_net_map.j2.yaml
index 9f9e331228..f22760c529 100644
--- a/network/service_net_map.j2.yaml
+++ b/network/service_net_map.j2.yaml
@@ -68,7 +68,9 @@ parameters:
       RabbitmqNetwork: {{ _service_nets.get('internal_api', 'ctlplane') }}
       QdrNetwork: {{ _service_nets.get('internal_api', 'ctlplane') }}
       RedisNetwork: {{ _service_nets.get('internal_api', 'ctlplane') }}
-      GaneshaNetwork: {{ _service_nets.get('storage_nfs', 'ctlplane') }}
+      # Guest VMs use GaneshaNetwork and cannot reach ctlplane network,
+      # so default to external when storage_nfs is not available.
+      GaneshaNetwork: {{ _service_nets.get('storage_nfs', 'external') }}
       MysqlNetwork: {{ _service_nets.get('internal_api', 'ctlplane') }}
       SnmpdNetwork: ctlplane
       CephClusterNetwork: {{ _service_nets.get('storage_mgmt', 'ctlplane') }}