CIDR functions for ARM templates
This article describes the functions for working with CIDR in your Azure Resource Manager template (ARM template).
Tip
We recommend Bicep because it offers the same capabilities as ARM templates and the syntax is easier to use. To learn more, see cidr functions.
parseCidr(network)
Parses an IP address range in CIDR notation to get various properties of the address range.
In Bicep, use the parseCidr function.
Parameter | Required | Type | Description |
---|---|---|---|
network | Yes | string | String in CIDR notation containing an IP address range to be converted. |
An object that contains various properties of the address range.
The following example parses an IPv4 CIDR string:
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"resources": [],
"outputs": {
"v4info": {
"type": "object",
"value": "[parseCidr('10.144.0.0/20')]"
}
}
}
The preceding example returns the following object:
{
"network":"10.144.0.0",
"netmask":"255.255.240.0",
"broadcast":"10.144.15.255",
"firstUsable":"10.144.0.1",
"lastUsable":"10.144.15.254",
"cidr":20
}
The following example parses an IPv6 CIDR string:
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"resources": [],
"outputs": {
"v6info": {
"type": "object",
"value": "[parseCidr('fdad:3236:5555::/48')]"
}
}
}
The preceding example returns the following object:
{
"network":"fdad:3236:5555::",
"netmask":"ffff:ffff:ffff::",
"firstUsable":"fdad:3236:5555::",
"lastUsable":"fdad:3236:5555:ffff:ffff:ffff:ffff:ffff",
"cidr":48
}
cidrSubnet(network, newCIDR, subnetIndex)
Splits the specified IP address range in CIDR notation into subnets with a new CIDR value and returns the IP address range of the subnet with the specified index.
In Bicep, use the cidrSubnet function.
Parameter | Required | Type | Description |
---|---|---|---|
network | Yes | string | String containing an IP address range to convert in CIDR notation. |
newCIDR | Yes | int | An integer representing the CIDR to be used to subnet. This value should be equal or larger than the CIDR value in the network parameter. |
subnetIndex | Yes | int | Index of the desired subnet IP address range to return. |
A string of the IP address range of the subnet with the specified index.
The following example calculates the first five /24 subnet ranges from the specified /20:
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"resources": [],
"outputs": {
"v4subnets": {
"type": "array",
"copy": {
"count": "[length(range(0, 5))]",
"input": "[cidrSubnet('10.144.0.0/20', 24, range(0, 5)[copyIndex()])]"
}
}
}
}
The preceding example returns the following array:
[
"10.144.0.0/24",
"10.144.1.0/24",
"10.144.2.0/24",
"10.144.3.0/24",
"10.144.4.0/24"
]
The following example calculates the first five /52 subnet ranges from the specified /48:
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"resources": [],
"outputs": {
"v6subnets": {
"type": "array",
"copy": {
"count": "[length(range(0, 5))]",
"input": "[cidrSubnet('fdad:3236:5555::/48', 52, range(0, 5)[copyIndex()])]"
}
}
}
}
The preceding example returns the following array:
[
"fdad:3236:5555::/52"
"fdad:3236:5555:1000::/52"
"fdad:3236:5555:2000::/52"
"fdad:3236:5555:3000::/52"
"fdad:3236:5555:4000::/52"
]
cidrHost(network, hostIndex)
Calculates the usable IP address of the host with the specified index on the specified IP address range in CIDR notation. For example, in the case of 192.168.1.0/24
, there are reserved IP addresses: 192.168.1.0
serves as the network identifier address, while 192.168.1.255
functions as the broadcast address. Only IP addresses ranging from 192.168.1.1
to 192.168.1.254
can be assigned to hosts, which are referred to as "usable" IP addresses. So, when the function is passed a hostIndex of 0
, 192.168.1.1
is returned.
In Bicep, use the cidrHost function.
Parameter | Required | Type | Description |
---|---|---|---|
network | Yes | string | String containing an ip network to convert (must be correct networking format). |
hostIndex | Yes | int | The index of the host IP address to return. |
A string of the IP address.
The following example calculates the first five usable host IP addresses from the specified /24:
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"resources": [],
"outputs": {
"v4hosts": {
"type": "array",
"copy": {
"count": "[length(range(0, 5))]",
"input": "[cidrHost('10.144.3.0/24', range(0, 5)[copyIndex()])]"
}
}
}
}
The preceding example returns the following array:
[
"10.144.3.1"
"10.144.3.2"
"10.144.3.3"
"10.144.3.4"
"10.144.3.5"
]
The following example calculates the first five usable host IP addresses from the specified /52:
{
"$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
"contentVersion": "1.0.0.0",
"resources": [],
"outputs": {
"v6hosts": {
"type": "array",
"copy": {
"count": "[length(range(0, 5))]",
"input": "[cidrHost('fdad:3236:5555:3000::/52', range(0, 5)[copyIndex()])]"
}
}
}
}
The preceding example returns the following array:
[
"fdad:3236:5555:3000::1"
"fdad:3236:5555:3000::2"
"fdad:3236:5555:3000::3"
"fdad:3236:5555:3000::4"
"fdad:3236:5555:3000::5"
]
- For a description of the sections in an ARM template, see Understand the structure and syntax of ARM templates.