diff --git a/ci/common/net-config-multinode-os-net-config.yaml b/ci/common/net-config-multinode-os-net-config.yaml
index 6e31088482..5b600c6910 100644
--- a/ci/common/net-config-multinode-os-net-config.yaml
+++ b/ci/common/net-config-multinode-os-net-config.yaml
@@ -37,9 +37,11 @@ parameters:
     default: ''
     description: IP address/subnet on the management network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   OvSBridgeMtu:
     default: 1300
diff --git a/ci/common/net-config-multinode.yaml b/ci/common/net-config-multinode.yaml
index 6ba9cb9ead..eb74a39e8c 100644
--- a/ci/common/net-config-multinode.yaml
+++ b/ci/common/net-config-multinode.yaml
@@ -37,9 +37,11 @@ parameters:
     default: ''
     description: IP address/subnet on the management network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
 
 resources:
diff --git a/ci/common/net-config-simple-bridge.yaml b/ci/common/net-config-simple-bridge.yaml
index bbc88862b5..f777d74fdb 100644
--- a/ci/common/net-config-simple-bridge.yaml
+++ b/ci/common/net-config-simple-bridge.yaml
@@ -6,9 +6,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ExternalIpSubnet:
     default: ''
diff --git a/ci/environments/network/multiple-nics-ipv6/network-environment.yaml b/ci/environments/network/multiple-nics-ipv6/network-environment.yaml
index 1960c712b3..be1d57aa2b 100644
--- a/ci/environments/network/multiple-nics-ipv6/network-environment.yaml
+++ b/ci/environments/network/multiple-nics-ipv6/network-environment.yaml
@@ -7,7 +7,6 @@ resource_registry:
   OS::TripleO::CephStorage::Net::SoftwareConfig: nic-configs/ceph-storage.yaml
 
 parameter_defaults:
-  ControlPlaneSubnetCidr: '24'
   ControlPlaneDefaultRoute: 192.168.24.1
   EC2MetadataIp: 192.168.24.1
   ExternalNetCidr: 2001:db8:fd00:1000::/64
diff --git a/ci/environments/network/multiple-nics-ipv6/nic-configs/ceph-storage.yaml b/ci/environments/network/multiple-nics-ipv6/nic-configs/ceph-storage.yaml
index 6a37859079..bfbfcc7e7b 100644
--- a/ci/environments/network/multiple-nics-ipv6/nic-configs/ceph-storage.yaml
+++ b/ci/environments/network/multiple-nics-ipv6/nic-configs/ceph-storage.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/multiple-nics-ipv6/nic-configs/cinder-storage.yaml b/ci/environments/network/multiple-nics-ipv6/nic-configs/cinder-storage.yaml
index 0bdbbba321..816accf974 100644
--- a/ci/environments/network/multiple-nics-ipv6/nic-configs/cinder-storage.yaml
+++ b/ci/environments/network/multiple-nics-ipv6/nic-configs/cinder-storage.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/multiple-nics-ipv6/nic-configs/compute.yaml b/ci/environments/network/multiple-nics-ipv6/nic-configs/compute.yaml
index d8a91325c7..157655e07e 100644
--- a/ci/environments/network/multiple-nics-ipv6/nic-configs/compute.yaml
+++ b/ci/environments/network/multiple-nics-ipv6/nic-configs/compute.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/multiple-nics-ipv6/nic-configs/controller.yaml b/ci/environments/network/multiple-nics-ipv6/nic-configs/controller.yaml
index cc54f76121..4df246f16e 100644
--- a/ci/environments/network/multiple-nics-ipv6/nic-configs/controller.yaml
+++ b/ci/environments/network/multiple-nics-ipv6/nic-configs/controller.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/multiple-nics-ipv6/nic-configs/swift-storage.yaml b/ci/environments/network/multiple-nics-ipv6/nic-configs/swift-storage.yaml
index 0bdbbba321..816accf974 100644
--- a/ci/environments/network/multiple-nics-ipv6/nic-configs/swift-storage.yaml
+++ b/ci/environments/network/multiple-nics-ipv6/nic-configs/swift-storage.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/multiple-nics/network-environment.yaml b/ci/environments/network/multiple-nics/network-environment.yaml
index 171adab680..6a9c160637 100644
--- a/ci/environments/network/multiple-nics/network-environment.yaml
+++ b/ci/environments/network/multiple-nics/network-environment.yaml
@@ -7,7 +7,6 @@ resource_registry:
   OS::TripleO::CephStorage::Net::SoftwareConfig: nic-configs/ceph-storage.yaml
 
 parameter_defaults:
-  ControlPlaneSubnetCidr: '24'
   ControlPlaneDefaultRoute: 192.168.24.1
   EC2MetadataIp: 192.168.24.1
   ExternalNetCidr: 10.0.0.0/24
diff --git a/ci/environments/network/multiple-nics/nic-configs/ceph-storage.yaml b/ci/environments/network/multiple-nics/nic-configs/ceph-storage.yaml
index 26de71f81e..5aa345bc36 100644
--- a/ci/environments/network/multiple-nics/nic-configs/ceph-storage.yaml
+++ b/ci/environments/network/multiple-nics/nic-configs/ceph-storage.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/multiple-nics/nic-configs/cinder-storage.yaml b/ci/environments/network/multiple-nics/nic-configs/cinder-storage.yaml
index ec036bbc6a..efb41bf2cb 100644
--- a/ci/environments/network/multiple-nics/nic-configs/cinder-storage.yaml
+++ b/ci/environments/network/multiple-nics/nic-configs/cinder-storage.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/multiple-nics/nic-configs/compute.yaml b/ci/environments/network/multiple-nics/nic-configs/compute.yaml
index 1da83cfd0b..f2a729a19c 100644
--- a/ci/environments/network/multiple-nics/nic-configs/compute.yaml
+++ b/ci/environments/network/multiple-nics/nic-configs/compute.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/multiple-nics/nic-configs/controller.yaml b/ci/environments/network/multiple-nics/nic-configs/controller.yaml
index 09c6d01be9..67ff1982fe 100644
--- a/ci/environments/network/multiple-nics/nic-configs/controller.yaml
+++ b/ci/environments/network/multiple-nics/nic-configs/controller.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/multiple-nics/nic-configs/swift-storage.yaml b/ci/environments/network/multiple-nics/nic-configs/swift-storage.yaml
index ec036bbc6a..efb41bf2cb 100644
--- a/ci/environments/network/multiple-nics/nic-configs/swift-storage.yaml
+++ b/ci/environments/network/multiple-nics/nic-configs/swift-storage.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/public-bond/network-environment.yaml b/ci/environments/network/public-bond/network-environment.yaml
index 6f451d6d11..905a876082 100644
--- a/ci/environments/network/public-bond/network-environment.yaml
+++ b/ci/environments/network/public-bond/network-environment.yaml
@@ -7,7 +7,6 @@ resource_registry:
   OS::TripleO::CephStorage::Net::SoftwareConfig: nic-configs/ceph-storage.yaml
 
 parameter_defaults:
-  ControlPlaneSubnetCidr: '24'
   ControlPlaneDefaultRoute: 192.168.24.1
   EC2MetadataIp: 192.168.24.1
   ExternalNetCidr: 10.0.0.0/24
diff --git a/ci/environments/network/public-bond/nic-configs/ceph-storage.yaml b/ci/environments/network/public-bond/nic-configs/ceph-storage.yaml
index 623c31e3d4..0f66ba81c8 100644
--- a/ci/environments/network/public-bond/nic-configs/ceph-storage.yaml
+++ b/ci/environments/network/public-bond/nic-configs/ceph-storage.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/public-bond/nic-configs/cinder-storage.yaml b/ci/environments/network/public-bond/nic-configs/cinder-storage.yaml
index 1cf2f6a3d1..441c84a37e 100644
--- a/ci/environments/network/public-bond/nic-configs/cinder-storage.yaml
+++ b/ci/environments/network/public-bond/nic-configs/cinder-storage.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/public-bond/nic-configs/compute.yaml b/ci/environments/network/public-bond/nic-configs/compute.yaml
index d4084aa867..e8bb722be9 100644
--- a/ci/environments/network/public-bond/nic-configs/compute.yaml
+++ b/ci/environments/network/public-bond/nic-configs/compute.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/public-bond/nic-configs/controller.yaml b/ci/environments/network/public-bond/nic-configs/controller.yaml
index 9ed1578c1a..968cd63835 100644
--- a/ci/environments/network/public-bond/nic-configs/controller.yaml
+++ b/ci/environments/network/public-bond/nic-configs/controller.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/ci/environments/network/public-bond/nic-configs/swift-storage.yaml b/ci/environments/network/public-bond/nic-configs/swift-storage.yaml
index 1cf2f6a3d1..441c84a37e 100644
--- a/ci/environments/network/public-bond/nic-configs/swift-storage.yaml
+++ b/ci/environments/network/public-bond/nic-configs/swift-storage.yaml
@@ -62,9 +62,11 @@ parameters:
     default: '10.0.0.1'
     description: default route for the external network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/deployed-server/deployed-server.yaml b/deployed-server/deployed-server.yaml
index 2f7d975b96..a777662fba 100644
--- a/deployed-server/deployed-server.yaml
+++ b/deployed-server/deployed-server.yaml
@@ -154,6 +154,10 @@ outputs:
     value:
       ctlplane:
         - {get_attr: [ControlPlanePort, fixed_ips, 0, ip_address]}
+  addresses:
+    value:
+      ctlplane:
+        - subnets: {get_attr: [ControlPlanePort, subnets]}
   name:
     value:
       yaql:
diff --git a/environments/network-environment-v6.j2.yaml b/environments/network-environment-v6.j2.yaml
index b3bbb5ea7e..041bc4966b 100644
--- a/environments/network-environment-v6.j2.yaml
+++ b/environments/network-environment-v6.j2.yaml
@@ -16,8 +16,12 @@ resource_registry:
 
 parameter_defaults:
   # This section is where deployment-specific configuration is done
-  # CIDR subnet mask length for provisioning network
-  ControlPlaneSubnetCidr: '24'
+  #
+  # NOTE: (Since Rocky)
+  # ControlPlaneSubnetCidr: It is no longer a requirement to provide this
+  #                         parameter. The attribute is resolved from the
+  #                         ctlplane subnet(s).
+  #
   # Gateway router for the provisioning network (or Undercloud IP)
   ControlPlaneDefaultRoute: 192.168.24.254
   EC2MetadataIp: 192.168.24.1  # Generally the IP of the Undercloud
diff --git a/environments/network-environment.j2.yaml b/environments/network-environment.j2.yaml
index 896eea40bd..a2adcfc32e 100644
--- a/environments/network-environment.j2.yaml
+++ b/environments/network-environment.j2.yaml
@@ -12,8 +12,12 @@ resource_registry:
 
 parameter_defaults:
   # This section is where deployment-specific configuration is done
-  # CIDR subnet mask length for provisioning network
-  ControlPlaneSubnetCidr: '24'
+  #
+  # NOTE: (Since Rocky)
+  # ControlPlaneSubnetCidr: It is no longer a requirement to provide the
+  #                         parameter. The attribute is resolved from the
+  #                         ctlplane subnet(s).
+  #
   # Gateway router for the provisioning network (or Undercloud IP)
   ControlPlaneDefaultRoute: 192.168.24.254
   EC2MetadataIp: 192.168.24.1  # Generally the IP of the Undercloud
diff --git a/net-config-bond.j2.yaml b/net-config-bond.j2.yaml
index 474a5f2e3d..da0b5a61fe 100644
--- a/net-config-bond.j2.yaml
+++ b/net-config-bond.j2.yaml
@@ -16,6 +16,12 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   {%- for network in networks %}
   {{network.name}}IpSubnet:
     default: ''
diff --git a/net-config-bridge.j2.yaml b/net-config-bridge.j2.yaml
index 3dc892b064..7ef75b86d3 100644
--- a/net-config-bridge.j2.yaml
+++ b/net-config-bridge.j2.yaml
@@ -6,6 +6,12 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   {%- for network in networks %}
   {{network.name}}IpSubnet:
     default: ''
diff --git a/net-config-linux-bridge.j2.yaml b/net-config-linux-bridge.j2.yaml
index 2f213fac7f..5f822628ca 100644
--- a/net-config-linux-bridge.j2.yaml
+++ b/net-config-linux-bridge.j2.yaml
@@ -16,6 +16,12 @@ parameters:
     description: The default route of the control plane network.
     type: string
     default: 192.168.24.1
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   EC2MetadataIp: # Override this via parameter_defaults
     description: The IP address of the EC2 metadata server.
     type: string
diff --git a/net-config-noop.j2.yaml b/net-config-noop.j2.yaml
index eca1387a73..2c032974e6 100644
--- a/net-config-noop.j2.yaml
+++ b/net-config-noop.j2.yaml
@@ -9,6 +9,12 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   {%- for network in networks %}
   {{network.name}}IpSubnet:
     default: ''
diff --git a/net-config-standalone.j2.yaml b/net-config-standalone.j2.yaml
index 5886300c2a..1e09c2ef16 100644
--- a/net-config-standalone.j2.yaml
+++ b/net-config-standalone.j2.yaml
@@ -13,9 +13,11 @@ parameters:
     description: IP address/subnet on the {{network.name_lower}} network
     type: string
   {%- endfor %}
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneStaticRoutes:
     default: []
diff --git a/net-config-static-bridge-with-external-dhcp.j2.yaml b/net-config-static-bridge-with-external-dhcp.j2.yaml
index 46d708a92b..8b047e957a 100644
--- a/net-config-static-bridge-with-external-dhcp.j2.yaml
+++ b/net-config-static-bridge-with-external-dhcp.j2.yaml
@@ -13,9 +13,11 @@ parameters:
     description: IP address/subnet on the {{network.name_lower}} network
     type: string
   {%- endfor %}
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/net-config-static-bridge.j2.yaml b/net-config-static-bridge.j2.yaml
index 92c759fad4..51d97653b0 100644
--- a/net-config-static-bridge.j2.yaml
+++ b/net-config-static-bridge.j2.yaml
@@ -13,9 +13,11 @@ parameters:
     description: IP address/subnet on the {{network.name_lower}} network
     type: string
   {%- endfor %}
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/net-config-static.j2.yaml b/net-config-static.j2.yaml
index 284aba215d..0cda610a75 100644
--- a/net-config-static.j2.yaml
+++ b/net-config-static.j2.yaml
@@ -12,9 +12,11 @@ parameters:
     description: IP address/subnet on the {{network.name_lower}} network
     type: string
   {%- endfor %}
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/net-config-undercloud.j2.yaml b/net-config-undercloud.j2.yaml
index 7c2c47f059..ea1c1882d8 100644
--- a/net-config-undercloud.j2.yaml
+++ b/net-config-undercloud.j2.yaml
@@ -13,9 +13,11 @@ parameters:
     description: IP address/subnet on the {{network.name_lower}} network
     type: string
   {%- endfor %}
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneStaticRoutes:
     default: []
diff --git a/network/config/bond-with-vlans/controller-no-external.j2.yaml b/network/config/bond-with-vlans/controller-no-external.j2.yaml
index a2e8643867..fa7eab7085 100644
--- a/network/config/bond-with-vlans/controller-no-external.j2.yaml
+++ b/network/config/bond-with-vlans/controller-no-external.j2.yaml
@@ -10,9 +10,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/config/bond-with-vlans/controller-v6.j2.yaml b/network/config/bond-with-vlans/controller-v6.j2.yaml
index 09e68e4499..e99003b2c0 100644
--- a/network/config/bond-with-vlans/controller-v6.j2.yaml
+++ b/network/config/bond-with-vlans/controller-v6.j2.yaml
@@ -8,9 +8,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/config/bond-with-vlans/role.role.j2.yaml b/network/config/bond-with-vlans/role.role.j2.yaml
index 939df167bc..0f63444016 100644
--- a/network/config/bond-with-vlans/role.role.j2.yaml
+++ b/network/config/bond-with-vlans/role.role.j2.yaml
@@ -6,9 +6,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/config/multiple-nics/compute-dvr.j2.yaml b/network/config/multiple-nics/compute-dvr.j2.yaml
index 634afd3564..eaec693b7b 100644
--- a/network/config/multiple-nics/compute-dvr.j2.yaml
+++ b/network/config/multiple-nics/compute-dvr.j2.yaml
@@ -8,9 +8,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/config/multiple-nics/controller-v6.j2.yaml b/network/config/multiple-nics/controller-v6.j2.yaml
index 5c4f58e426..942bd19976 100644
--- a/network/config/multiple-nics/controller-v6.j2.yaml
+++ b/network/config/multiple-nics/controller-v6.j2.yaml
@@ -7,9 +7,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/config/multiple-nics/role.role.j2.yaml b/network/config/multiple-nics/role.role.j2.yaml
index 74b3fcef95..6f4e549989 100644
--- a/network/config/multiple-nics/role.role.j2.yaml
+++ b/network/config/multiple-nics/role.role.j2.yaml
@@ -6,9 +6,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/config/single-nic-linux-bridge-vlans/controller-v6.j2.yaml b/network/config/single-nic-linux-bridge-vlans/controller-v6.j2.yaml
index bc7a0f35ba..3e110b4d74 100644
--- a/network/config/single-nic-linux-bridge-vlans/controller-v6.j2.yaml
+++ b/network/config/single-nic-linux-bridge-vlans/controller-v6.j2.yaml
@@ -7,9 +7,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/config/single-nic-linux-bridge-vlans/role.role.j2.yaml b/network/config/single-nic-linux-bridge-vlans/role.role.j2.yaml
index 4c6d11d3e3..8cd866c2d2 100644
--- a/network/config/single-nic-linux-bridge-vlans/role.role.j2.yaml
+++ b/network/config/single-nic-linux-bridge-vlans/role.role.j2.yaml
@@ -6,9 +6,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/config/single-nic-vlans/controller-no-external.j2.yaml b/network/config/single-nic-vlans/controller-no-external.j2.yaml
index a652c74525..0c785c81fe 100644
--- a/network/config/single-nic-vlans/controller-no-external.j2.yaml
+++ b/network/config/single-nic-vlans/controller-no-external.j2.yaml
@@ -10,9 +10,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/config/single-nic-vlans/controller-v6.j2.yaml b/network/config/single-nic-vlans/controller-v6.j2.yaml
index e7ff280b8c..84edced4d4 100644
--- a/network/config/single-nic-vlans/controller-v6.j2.yaml
+++ b/network/config/single-nic-vlans/controller-v6.j2.yaml
@@ -7,9 +7,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/config/single-nic-vlans/role.role.j2.yaml b/network/config/single-nic-vlans/role.role.j2.yaml
index f5bcaa56ef..e043c0600a 100644
--- a/network/config/single-nic-vlans/role.role.j2.yaml
+++ b/network/config/single-nic-vlans/role.role.j2.yaml
@@ -6,9 +6,11 @@ parameters:
     default: ''
     description: IP address/subnet on the ctlplane network
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   ControlPlaneDefaultRoute: # Override this via parameter_defaults
     description: The default route of the control plane network.
diff --git a/network/ports/ctlplane_vip.yaml b/network/ports/ctlplane_vip.yaml
index 51934104f8..4d3aa589f7 100644
--- a/network/ports/ctlplane_vip.yaml
+++ b/network/ports/ctlplane_vip.yaml
@@ -21,6 +21,12 @@ parameters:
     description: IP address on the control plane
     default: ''
     type: string
+  ControlPlaneSubnetCidr: # Here for compatibility with ctlplane_vip.yaml
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   ControlPlaneNetwork:
     description: The name of the undercloud Neutron control plane
     default: ctlplane
diff --git a/network/ports/from_service.yaml b/network/ports/from_service.yaml
index 5f07d061d1..d9140c716d 100644
--- a/network/ports/from_service.yaml
+++ b/network/ports/from_service.yaml
@@ -20,6 +20,12 @@ parameters:
     description: IP address on the control plane
     default: ''
     type: string
+  ControlPlaneSubnetCidr: # Here for compatibility with ctlplane_vip.yaml
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   ControlPlaneNetwork: # Here for compatibility with ctlplane_vip.yaml
     description: The name of the undercloud Neutron control plane
     default: ctlplane
diff --git a/network/ports/from_service_v6.yaml b/network/ports/from_service_v6.yaml
index cc01620c00..2047ef9576 100644
--- a/network/ports/from_service_v6.yaml
+++ b/network/ports/from_service_v6.yaml
@@ -20,6 +20,12 @@ parameters:
     description: IP address on the control plane
     default: ''
     type: string
+  ControlPlaneSubnetCidr: # Here for compatibility with ctlplane_vip.yaml
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   ControlPlaneNetwork: # Here for compatability with ctlplane_vip.yaml
     description: The name of the undercloud Neutron control plane
     default: ctlplane
diff --git a/network/ports/net_ip_map.j2.yaml b/network/ports/net_ip_map.j2.yaml
index 8046873c1b..d8e4cdfb2a 100644
--- a/network/ports/net_ip_map.j2.yaml
+++ b/network/ports/net_ip_map.j2.yaml
@@ -4,9 +4,11 @@ parameters:
   ControlPlaneIp:
     default: ''
     type: string
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
 {%- for network in networks %}
   {{network.name}}Ip:
diff --git a/network/ports/noop.yaml b/network/ports/noop.yaml
index c9569f5362..740a8cf736 100644
--- a/network/ports/noop.yaml
+++ b/network/ports/noop.yaml
@@ -33,9 +33,11 @@ parameters:
         [{'ip_address':'1.2.3.4'}]
     default: []
     type: json
-  ControlPlaneSubnetCidr: # Override this via parameter_defaults
-    default: '24'
-    description: The subnet CIDR of the control plane network.
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
     type: string
   IPPool: # Here for compatibility with from_pool.yaml
     default: {}
diff --git a/network/ports/port.j2 b/network/ports/port.j2
index 079646d95f..a60d944e2a 100644
--- a/network/ports/port.j2
+++ b/network/ports/port.j2
@@ -17,6 +17,12 @@ parameters:
     description: IP address on the control plane
     default: ''
     type: string
+  ControlPlaneSubnetCidr: # Here for compatibility with noop.yaml
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   ControlPlaneNetwork: # Here for compatibility with ctlplane_vip.yaml
     description: The name of the undercloud Neutron control plane
     default: ctlplane
diff --git a/network/ports/port_from_pool.j2 b/network/ports/port_from_pool.j2
index caaa2de331..1fa2f97a29 100644
--- a/network/ports/port_from_pool.j2
+++ b/network/ports/port_from_pool.j2
@@ -28,6 +28,12 @@ parameters:
     description: IP address on the control plane
     default: ''
     type: string
+  ControlPlaneSubnetCidr: # Here for compatibility with noop.yaml
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
+    default: ''
   ControlPlaneNetwork: # Here for compatibility with ctlplane_vip.yaml
     description: The name of the undercloud Neutron control plane
     default: ctlplane
diff --git a/network/ports/vip.yaml b/network/ports/vip.yaml
index 0b29ac22a6..4cbe70ce43 100644
--- a/network/ports/vip.yaml
+++ b/network/ports/vip.yaml
@@ -21,6 +21,12 @@ parameters:
     description: IP address on the control plane
     default: ''
     type: string
+  ControlPlaneSubnetCidr: # Here for compatibility with noop.yaml
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   ControlPlaneNetwork:
     description: The name of the undercloud Neutron control plane
     default: ctlplane
diff --git a/network/ports/vip_v6.yaml b/network/ports/vip_v6.yaml
index a6042c6fee..6cc5510d3e 100644
--- a/network/ports/vip_v6.yaml
+++ b/network/ports/vip_v6.yaml
@@ -21,6 +21,12 @@ parameters:
     description: IP address on the control plane
     default: ''
     type: string
+  ControlPlaneSubnetCidr: # Here for compatibility with noop.yaml
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   ControlPlaneNetwork:
     description: The name of the undercloud Neutron control plane
     default: ctlplane
diff --git a/overcloud.j2.yaml b/overcloud.j2.yaml
index 30f5fe94e3..d887ab4347 100644
--- a/overcloud.j2.yaml
+++ b/overcloud.j2.yaml
@@ -98,6 +98,12 @@ parameters:
     description: The name of the undercloud Neutron control plane subnet
     default: ctlplane-subnet
     type: string
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
   ControlFixedIPs:
     default: []
     description: >
@@ -260,6 +266,9 @@ parameter_groups:
 conditions:
   add_vips_to_etc_hosts: {equals : [{get_param: AddVipsToEtcHosts}, True]}
   control_fixed_ip_not_set: {equals : [{get_param: ControlFixedIPs}, []]}
+  ctlplane_subnet_cidr_set:
+    not:
+      equals: [{get_param: ControlPlaneSubnetCidr}, '']
 
 resources:
 
@@ -777,6 +786,11 @@ resources:
     type: OS::TripleO::Network::Ports::RedisVipPort
     properties:
       ControlPlaneIP: {get_attr: [ControlVirtualIP, fixed_ips, 0, ip_address]}
+      ControlPlaneSubnetCidr:
+        if:
+          - ctlplane_subnet_cidr_set
+          - {get_param: ControlPlaneSubnetCidr}
+          - {str_split: ['/', {get_attr: [ControlVirtualIP, subnets, 0, cidr]}, 1]}
       ControlPlaneNetwork: {get_param: NeutronControlPlaneID}
       PortName: redis_virtual_ip
       NetworkName: {get_attr: [ServiceNetMap, service_net_map, RedisNetwork]}
@@ -791,6 +805,11 @@ resources:
     type: OS::TripleO::Network::Ports::ExternalVipPort
     properties:
       ControlPlaneIP: {get_attr: [ControlVirtualIP, fixed_ips, 0, ip_address]}
+      ControlPlaneSubnetCidr:
+        if:
+          - ctlplane_subnet_cidr_set
+          - {get_param: ControlPlaneSubnetCidr}
+          - {str_split: ['/', {get_attr: [ControlVirtualIP, subnets, 0, cidr]}, 1]}
       ControlPlaneNetwork: {get_param: NeutronControlPlaneID}
       PortName: public_virtual_ip
       FixedIPs: {get_param: PublicVirtualFixedIPs}
@@ -800,6 +819,11 @@ resources:
     type: OS::TripleO::Network::Ports::{{network.name}}VipPort
     properties:
       ControlPlaneIP: {get_attr: [ControlVirtualIP, fixed_ips, 0, ip_address]}
+      ControlPlaneSubnetCidr:
+        if:
+          - ctlplane_subnet_cidr_set
+          - {get_param: ControlPlaneSubnetCidr}
+          - {str_split: ['/', {get_attr: [ControlVirtualIP, subnets, 0, cidr]}, 1]}
       PortName: {{network.name_lower}}_virtual_ip
       FixedIPs: {get_param: {{network.name}}VirtualFixedIPs}
 {%- endif %}
@@ -809,6 +833,11 @@ resources:
     type: OS::TripleO::Network::Ports::NetVipMap
     properties:
       ControlPlaneIp: {get_attr: [ControlVirtualIP, fixed_ips, 0, ip_address]}
+      ControlPlaneSubnetCidr:
+        if:
+          - ctlplane_subnet_cidr_set
+          - {get_param: ControlPlaneSubnetCidr}
+          - {str_split: ['/', {get_attr: [ControlVirtualIP, subnets, 0, cidr]}, 1]}
 {%- for network in networks if network.vip|default(false) %}
 {%- if network.name == 'External' %}
       ExternalIp: {get_attr: [PublicVirtualIP, ip_address]}
diff --git a/puppet/role.role.j2.yaml b/puppet/role.role.j2.yaml
index 8dcf0df7fc..87785e661d 100644
--- a/puppet/role.role.j2.yaml
+++ b/puppet/role.role.j2.yaml
@@ -244,6 +244,12 @@ parameters:
   {{role.name}}MaxFailPercentage:
     default: 15
     type: number
+  ControlPlaneSubnetCidr:
+    default: ''
+    description: >
+      The subnet CIDR of the control plane network. (The parameter is
+      automatically resolved from the ctlplane subnet's cidr attribute.)
+    type: string
 
   ServerDeletionPolicy:
     description: Whether to retain or delete servers on deletion of the stack
@@ -315,6 +321,9 @@ conditions:
         - {get_param: [{{role.name}}IPs, '{{network.name_lower}}', {get_param: NodeIndex}]}
         - ''
 {%- endfor %}
+  ctlplane_subnet_cidr_set:
+    not:
+      equals: [{get_param: ControlPlaneSubnetCidr}, '']
 
 resources:
   {{server_resource_name}}:
@@ -424,6 +433,11 @@ resources:
           - {{role.name}}_{{network.name}}_fixed_ip_set
           - [{ip_address: {get_param: [{{role.name}}IPs, '{{network.name_lower}}', {get_param: NodeIndex}]}}]
           - []
+      ControlPlaneSubnetCidr:
+        if:
+          - ctlplane_subnet_cidr_set
+          - {get_param: ControlPlaneSubnetCidr}
+          - {str_split: ['/', {get_attr: [{{server_resource_name}}, addresses, ctlplane, 0, subnets, 0, cidr]}, 1]}
       IPPool:
         map_merge:
 {%- if role.deprecated_param_ips is defined %}
@@ -437,6 +451,11 @@ resources:
     type: OS::TripleO::{{role.name}}::Net::SoftwareConfig
     properties:
       ControlPlaneIp: {get_attr: [{{server_resource_name}}, networks, ctlplane, 0]}
+      ControlPlaneSubnetCidr:
+        if:
+          - ctlplane_subnet_cidr_set
+          - {get_param: ControlPlaneSubnetCidr}
+          - {str_split: ['/', {get_attr: [{{server_resource_name}}, addresses, ctlplane, 0, subnets, 0, cidr]}, 1]}
   {%- for network in networks %}
       {{network.name}}IpSubnet: {get_attr: [{{network.name}}Port, ip_subnet]}
   {%- endfor %}
@@ -445,6 +464,11 @@ resources:
     type: OS::TripleO::Network::Ports::NetIpMap
     properties:
       ControlPlaneIp: {get_attr: [{{server_resource_name}}, networks, ctlplane, 0]}
+      ControlPlaneSubnetCidr:
+        if:
+          - ctlplane_subnet_cidr_set
+          - {get_param: ControlPlaneSubnetCidr}
+          - {str_split: ['/', {get_attr: [{{server_resource_name}}, addresses, ctlplane, 0, subnets, 0, cidr]}, 1]}
   {%- for network in networks %}
       {{network.name}}Ip: {get_attr: [{{network.name}}Port, ip_address]}
       {{network.name}}IpSubnet: {get_attr: [{{network.name}}Port, ip_subnet]}
@@ -753,6 +777,8 @@ outputs:
         - hostname:
             fixed_ips:
               - ip_address: {get_attr: [{{server_resource_name}}, networks, ctlplane, 0]}
+            subnets:
+              - cidr: {get_attr: [{{server_resource_name}}, addresses, ctlplane, 0, subnets, 0, cidr]}
         - keys:
             hostname:
               list_join:
diff --git a/releasenotes/notes/use-subnet-attrs-ctlplane-cidr-a02e14a251733726.yaml b/releasenotes/notes/use-subnet-attrs-ctlplane-cidr-a02e14a251733726.yaml
new file mode 100644
index 0000000000..e5fb486f46
--- /dev/null
+++ b/releasenotes/notes/use-subnet-attrs-ctlplane-cidr-a02e14a251733726.yaml
@@ -0,0 +1,25 @@
+---
+features:
+  - |
+    It is no longer a requirement to provide the parameter:
+    ``ControlPlaneSubnetCidr``  in the environment when deploying. Now
+    ``get_attr`` on the server resource is used to resolve the value from the
+    ``ctlplane`` subnet's ``cidr`` attribute. A conditional is used to
+    determine if the user provided the parameter in the environment. If the
+    user provided the parameter, the user provided value is used.
+upgrade:
+  - |
+    Since the the ``ControlPlaneSubnetCidr`` can now be resolved from the
+    ``ctlplane`` subnet(s) this parameter can be removed from the environment
+    (``network-environment.yaml``).
+
+    .. Note:: Prior to removing the parameter, ensure that the property of
+              the ``ctlplane`` subnet(s) is correct. In case it is not, update
+              ``undercloud.conf`` with the correct configuration and re-run the
+              ``openstack undercloud install`` command to ensure the property
+              is set correctly.
+
+    .. Note:: ``ControlPlaneSubnetCidr`` is now passed to the network config
+              template when the resource is created. Because of this the
+              parameter must be defined in the network config template, even if
+              it is not used.