Improve IP CIDR generation

docker/network/subnet.tf

@@ -1,14 +1,24 @@
-resource "random_integer" "upper_mid_byte" {
-  min = 18
-  max = 31
+locals {
+  ranges = {
+    "low" = {
+      "min" = 18
+      "max" = 31
+    }
+    "high" = {
+      "min" = 128
+      "max" = 255
+    }
+  }
 }
-resource "random_integer" "lower_mid_byte" {
-  min = 10
-  max = 254
+resource "random_integer" "subnet_ip_octet" {
+  for_each = local.ranges
+  min      = local.ranges[each.key].min
+  max      = local.ranges[each.key].max
 }
+
 locals {
   // Generate a subnet
-  subnet = var.subnet != null ? var.subnet : "172.${random_integer.upper_mid_byte.result}.${random_integer.lower_mid_byte.result}.0/24"
+  subnet = var.subnet != null ? var.subnet : "172.${random_integer.subnet_ip_octet["high"].result}.${random_integer.subnet_ip_octet["low"].result}.0/24"
   // Calculate the gateway from the subnet
   gateway = cidrhost(local.subnet, 1)
 }