diff --git a/src/domains/citizen-auth-app/01_network.tf b/src/domains/citizen-auth-app/01_network.tf
index 4a4e5d44d..155b75b9a 100644
--- a/src/domains/citizen-auth-app/01_network.tf
+++ b/src/domains/citizen-auth-app/01_network.tf
@@ -74,6 +74,12 @@ data "azurerm_subnet" "app_backend_l2_snet" {
   resource_group_name  = local.vnet_common_resource_group_name
 }
 
+data "azurerm_subnet" "app_backend_l3_snet" {
+  name                 = "appbackendl3"
+  virtual_network_name = local.vnet_common_name
+  resource_group_name  = local.vnet_common_resource_group_name
+}
+
 data "azurerm_subnet" "ioweb_profile_snet" {
   name                 = format("%s-ioweb-profile-snet", local.common_project)
   virtual_network_name = local.vnet_common_name
diff --git a/src/domains/citizen-auth-app/07_function_fast_login.tf b/src/domains/citizen-auth-app/07_function_fast_login.tf
index b50797eb2..7646f546f 100644
--- a/src/domains/citizen-auth-app/07_function_fast_login.tf
+++ b/src/domains/citizen-auth-app/07_function_fast_login.tf
@@ -273,6 +273,7 @@ module "function_fast_login" {
     data.azurerm_subnet.app_backend_l2_snet.id,
     data.azurerm_subnet.ioweb_profile_snet.id,
     module.session_manager_snet.id,
+    data.azurerm_subnet.app_backend_l3_snet.id
   ]
 
   # Action groups for alerts
@@ -321,7 +322,8 @@ module "function_fast_login_staging_slot" {
     data.azurerm_subnet.azdoa_snet[0].id,
     data.azurerm_subnet.apim_v2_snet.id,
     data.azurerm_subnet.app_backend_l1_snet.id,
-    data.azurerm_subnet.app_backend_l2_snet.id
+    data.azurerm_subnet.app_backend_l2_snet.id,
+    data.azurerm_subnet.app_backend_l3_snet.id
   ]
 
   tags = var.tags
diff --git a/src/domains/citizen-auth-app/README.md b/src/domains/citizen-auth-app/README.md
index 4bae09cc3..c2dc1641f 100644
--- a/src/domains/citizen-auth-app/README.md
+++ b/src/domains/citizen-auth-app/README.md
@@ -154,6 +154,7 @@
 | [azurerm_subnet.apim_v2_snet](https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/data-sources/subnet) | data source |
 | [azurerm_subnet.app_backend_l1_snet](https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/data-sources/subnet) | data source |
 | [azurerm_subnet.app_backend_l2_snet](https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/data-sources/subnet) | data source |
+| [azurerm_subnet.app_backend_l3_snet](https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/data-sources/subnet) | data source |
 | [azurerm_subnet.appgateway_snet](https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/data-sources/subnet) | data source |
 | [azurerm_subnet.azdoa_snet](https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/data-sources/subnet) | data source |
 | [azurerm_subnet.fims_op_app_snet_01](https://registry.terraform.io/providers/hashicorp/azurerm/latest/docs/data-sources/subnet) | data source |
diff --git a/src/domains/functions/data.tf b/src/domains/functions/data.tf
index 67877d5a7..2674b6e1e 100644
--- a/src/domains/functions/data.tf
+++ b/src/domains/functions/data.tf
@@ -187,3 +187,9 @@ data "azurerm_subnet" "app_backendl2_snet" {
   resource_group_name  = local.rg_common_name
   virtual_network_name = local.vnet_common_name
 }
+
+data "azurerm_subnet" "app_backendl3_snet" {
+  name                 = "appbackendl3"
+  resource_group_name  = local.rg_common_name
+  virtual_network_name = local.vnet_common_name
+}
diff --git a/src/domains/functions/function_app.tf b/src/domains/functions/function_app.tf
index c086e8482..de0cd2fee 100644
--- a/src/domains/functions/function_app.tf
+++ b/src/domains/functions/function_app.tf
@@ -239,6 +239,7 @@ module "function_app" {
     data.azurerm_subnet.app_backendli_snet.id,
     data.azurerm_subnet.ioweb_profile_snet.id,
     data.azurerm_subnet.session_manager_snet.id,
+    data.azurerm_subnet.app_backendl3_snet.id
   ]
 
   sticky_app_setting_names = concat([
@@ -291,6 +292,7 @@ module "function_app_staging_slot" {
     data.azurerm_subnet.app_backendl1_snet.id,
     data.azurerm_subnet.app_backendl2_snet.id,
     data.azurerm_subnet.app_backendli_snet.id,
+    data.azurerm_subnet.app_backendl3_snet.id
   ]
 
   tags = var.tags