Configure alias IP ranges

This document contains instructions for configuring alias IP addresses and alias IP ranges by using the Google Cloud console and the Google Cloud CLI. Before executing these commands, review Alias IP ranges.

Limitations

Subnet

The per network limits describe the maximum number of secondary ranges that you can define for each subnet.
You cannot add and remove secondary ranges at the same time. Adding and removing must be done as separate steps.
CIDR expansion is not supported for secondary ranges.

VM instance

Alias IP ranges are supported on all VM network interfaces. Routing is configured automatically for alias IP ranges on the primary network interface, but not secondary interfaces. If you have multiple network interfaces, you must configure policy routing for the additional interfaces. For an example of how to do this, see the following tutorial: Configure routing to a secondary interface of a VM.
Alias IP ranges can be added or deleted, but they can't be updated.
If you remove an alias IP range from one VM and assign it to another VM, it might take up to a minute for the transfer to complete.
Firewall source tags are not supported for alias IP addresses. This means that when you configure source tags in firewall rules, the source tags match the VM primary IP address, but not the alias IP addresses. Use source ranges to allow or deny ingress traffic from alias IP addresses.
Internal DNS resolves a VM name to its primary IP. Additional names for alias IPs are not configured automatically, but might be added manually.

VPC network

Adding or removing a large number of alias IP ranges at the same time can take a long time. For example, it might take up to 10 minutes to add or delete 7000 alias IP ranges.
Auto mode VPC networks cannot be deleted if secondary subnet ranges are present.
In a static route, the next-hop IP address must be the primary IP address of the VM. Alias IP addresses are not supported as next-hop IP addresses.
IPv6 addresses are not supported.
Alias IP ranges are only supported in VPC networks, not legacy networks. To determine your network type, list your networks. VPC networks have a mode of custom or auto. Legacy networks have a mode of legacy.

Subnet commands

VM alias IP ranges must be assigned from a range owned by the subnet that the VM is in. All subnets have a primary range, which is the standard range of internal IP addresses that defines the subnet. A subnet might also have one or more secondary IP ranges of internal IP addresses. You can assign alias IP ranges from either the primary or secondary ranges of the subnet.

You must give each secondary range a name that is unique for the subnet. When assigning an alias IP range to a VM, the secondary range name tells Google Cloud from which subnet range to assign the alias IPs.

All ranges, both primary and secondary, must be unique across all subnets in the VPC network and in any networks attached via VPC Network Peering, VPN, or Interconnect.

This section shows you how to create a subnet with a secondary range, add a secondary range to an existing subnet, or remove a secondary range from a subnet. Once your subnet has the range you want to use, see the VM instance commands for instructions on assigning a range to a VM.

Create a subnet with one or more secondary CIDR ranges

This command assumes you have a VPC network already. If you do not, create one.

This command is the same whether you're creating a subnet for the VM's primary interface or one of the secondary interfaces.

Using a secondary range for alias IP allocation allows you to separate the IP space for services hosted in the VM, making it easier to create firewall rules that allow access only to the services running on the VM and block access to the VM's primary IP address.

Console

Go to the VPC networks page in the Google Cloud console.
Go to the VPC networks page
Click the name of an existing network.
Click Add subnet.
Enter a Name for the new subnet.
Specify the Region.
Enter an IP address range in CIDR notation. (Example: 10.65.61.0/24)
Click Create secondary IP range.
Enter a Subnet range name.
Enter a Secondary IP range in CIDR notation. (Example: 10.9.0.0/24)
To add additional secondary IP ranges, for each range click Add IP range, then provide a name and range.
Click Add.

gcloud

gcloud compute networks subnets create s1 \
    --network NETWORK_NAME \
    --region REGION \
    --range 10.65.61.0/24 \
    --secondary-range RANGE_NAME_1=RANGE_CIDR_1,RANGE_NAME_2=RANGE_CIDR_2,...

Replace the following:

NETWORK_NAME: the name of the network where you want to create the subnet.
REGION: the region where you are creating the subnet.
RANGE_NAME_1=RANGE_CIDR_1 and RANGE_NAME_2=RANGE_CIDR_2: the names of the secondary ranges from which to draw the alias IP ranges and the alias IP range itself—for example, range1=10.9.0.0/24.

For the complete syntax, see the gcloud CLI documentation.

API

Create a subnet with one or more secondary ranges.

POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/subnetworks
{
  "ipCidrRange": "PRIMARY_IP_RANGE",
  "network": "NETWORK_URL",
  "name": "SUBNET_NAME",
  "secondaryIpRanges": [
  {
    "rangeName": "SECONDARY_RANGE_NAME_1",
    "ipCidrRange": "SECONDARY_IP_RANGE_1"
  },
  {
    "rangeName": "SECONDARY_RANGE_NAME_2",
    "ipCidrRange": "SECONDARY_IP_RANGE_2"
  },
  ...]
}

Replace the following:

NETWORK_URL: the URL or the VPC network where the subnet will be created.
PRIMARY_IP_RANGE: the primary IP address range for the subnet.
PROJECT_ID: the ID of the project that contains the VPC network where the subnet will be created.
REGION: the region where the subnet will be located.
SECONDARY_IP_RANGE_1 and SECONDARY_IP_RANGE_2: the IP address ranges to use for the secondary ranges.
SECONDARY_RANGE_NAME_1 and SECONDARY_RANGE_NAME_2: the names to use for the secondary ranges.
SUBNET_NAME: a name for the subnet.

For more information, see the subnetworks.insert method.

Terraform

You can use the Terraform resource to create a subnet with one or more secondary ranges.

The Terraform arguments have example values that you can change.

resource "google_compute_subnetwork" "network-with-private-secondary-ip-ranges" {
  project       = var.project_id # Replace this with your project ID in quotes
  name          = "test-subnetwork"
  ip_cidr_range = "10.2.0.0/16"
  region        = "us-central1"
  network       = "test-vpc-network"
  secondary_ip_range {
    range_name    = "tf-test-secondary-range-update1"
    ip_cidr_range = "192.168.10.0/24"
  }
}

To learn how to apply or remove a Terraform configuration, see Basic Terraform commands.

Add secondary CIDR ranges to an existing subnet

This procedure assumes you have a subnet that you want to use, but you need to add one or more secondary ranges.

Using a secondary range for alias IP allocation makes it easier to create firewall rules that allow access to the services running on a VM, but not to the VM's primary IP address.

Console

Go to the VPC networks page in the Google Cloud console.
Go to the VPC networks page
Click the name of a subnet to modify to view its details page.
Click Edit.
In the Secondary IP ranges section, click Add IP range.
Enter a name for Subnet range name.
Enter a range for Secondary IP range in CIDR notation. (Example: 10.9.0.0/24)
To add additional secondary IP ranges, for each range click Add IP range, then provide a name and range.
Click Save.

gcloud

gcloud compute networks subnets update SUBNET_NAME \
    --region REGION \
    --add-secondary-ranges RANGE_NAME_1=RANGE_CIDR_1,RANGE_NAME_2=RANGE_CIDR_2,...

Replace the following:

SUBNET_NAME: the name of the subnet that you want to add the secondary ranges to.
REGION: the region where you are creating the subnet.
RANGE_NAME_1=RANGE_CIDR_1 and RANGE_NAME_2=RANGE_CIDR_2: the names of the secondary ranges from which to draw the alias IP ranges and the alias IP range itself—for example, range1=10.9.0.0/24.

For the complete syntax, see the gcloud CLI documentation.

API

Add a secondary range to an existing subnet.

PATCH https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/subnetworks/SUBNET_NAME
{
  "secondaryIpRanges": [
  {
    "rangeName": "SECONDARY_RANGE_NAME_1",
    "ipCidrRange": "SECONDARY_IP_RANGE_1"
  },
  {
    "rangeName": "SECONDARY_RANGE_NAME_2",
    "ipCidrRange": "SECONDARY_IP_RANGE_2"
  },
  ...],
  "fingerprint": "SUBNETWORK_FINGERPRINT"
}

Replace the placeholders with valid values:

PROJECT_ID is the ID of the project that contains the subnet to modify.
REGION is the region where the subnet is located.
SECONDARY_IP_RANGE_1 and SECONDARY_IP_RANGE_2 are the IP address ranges to use for the secondary ranges.
SECONDARY_RANGE_NAME_1 and SECONDARY_RANGE_NAME_2 are the names to use for the secondary ranges
SUBNET_FINGERPRINT is the finger print ID for the existing subnet, which is provided when you describe a subnet.
SUBNET_NAME is the name of the subnet to modify.

For more information, see the subnetworks.patch method.

Remove a secondary CIDR range from a subnet

You can remove existing secondary ranges from a subnet. To view the ranges that are associated with a subnet, see Describe a subnet.

Console

Go to the VPC networks page in the Google Cloud console.
Go to the VPC networks page
Click the name of a subnet to modify to view its details page.
Click Edit.
In the Secondary IP ranges section, click X next to the secondary range to remove.
Click Save.

gcloud

gcloud compute networks subnets update SUBNET_NAME \
    --region REGION \
    --remove-secondary-ranges RANGE_NAME_1,RANGE_NAME_2,...

where

SUBNET_NAME is the name of the subnet that you want to remove the secondary ranges from.
REGION the region where you are creating the subnet.
RANGE_NAME_1 and RANGE_NAME_2 are the names of the secondary ranges that will be removed from the target subnet SUBNET_NAME—for example, range1=10.9.0.0/24.

For the complete syntax, see the gcloud CLI documentation.

API

Exclude secondary ranges to remove them. The following example removes all secondary ranges from an existing subnet:

PATCH https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/regions/REGION/subnetworks/SUBNET_NAME
{
  "fingerprint": "SUBNET_FINGERPRINT",
  "secondaryIpRanges": [
  ]
}

Replace the placeholders with valid values:

PROJECT_ID is the ID of the project that contains the subnet to modify.
REGION is the region where the subnet is located.
SUBNET_FINGERPRINT is the finger print ID for the existing subnet, which is provided when you describe a subnet.
SUBNET_NAME is the name of the subnet to modify.

For more information, see the subnetworks.patch method.

Work with VM instances

These commands show how to create an instance with an alias IP range, add one or more alias IP ranges to an existing VM instance, or remove one or more ranges from an existing VM instance.

Create a VM with an alias IP range in the primary CIDR range

Use this procedure if you want to assign an alias IP range from the primary range of the subnet. The range you choose must not already be in use, even in part, by any other resource on the VPC network.

Use this procedure if you want the instance's primary interface and alias IP addresses to be in the same range.

Console

Go to the VM instances page in the Google Cloud console.
Go to the VM instances page
Click Create instance.
Enter a Name for the new instance.
Specify a Zone.
Click Management, security, disks, networking, sole tenancy.
Click the Networking tab.
Click the edit (pencil icon) button next to the primary interface in the Network interfaces section.
Click Show alias IP ranges.
Leave Subnet range set to Primary.
Enter an Alias IP range in CIDR notation. This range must be an unused subrange of the primary range.
Click Create.

gcloud

gcloud compute instances create vm1 \
    --zone ZONE \
    --network-interface "subnet=SUBNET_NAME,aliases=RANGE_CIDR_1;RANGE_CIDR_2,..."

where

ZONE the zone that will contain the instance.
SUBNET_NAME is the name of the subnet that will contain the instance.
RANGE_CIDR_1 and RANGE_CIDR_2 are the IP ranges from the primary subnet to assign to the interface. The ranges can be a specific range (192.168.100.0/24), a single IP address (192.168.100.1), or a netmask in CIDR format (/24). If the IP range is specified by netmask only, the IP allocator chooses an available range with the specified netmask and allocates it to the network interface. To specify more than one range, separate the ranges with semicolons (;).

For the complete syntax, see the gcloud CLI documentation.

API

Create an instance with an alias IP address from the primary IP address range of the instance's subnet.

POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances
{
  "networkInterfaces": [
    {
      "aliasIpRanges": [
        {
          "ipCidrRange": "CIDR_RANGE"
        }
      ]
    },
    ...
  ],
  ...
}

Replace the placeholders with valid values:

PROJECT_ID is the ID of the project where you create the instance.
CIDR_RANGE is the IP range from the primary subnet to assign to the interface. The range can be a specific range (192.168.100.0/24), a single IP address (192.168.100.1), or a net mask in CIDR format (/24). If you specify the IP range by netmask only, the IP address allocator chooses an available range with the specified netmask and assigns it to the network interface.
ZONE is the Google Cloud zone where the instance will be created.

For more information, see the instance.insert method.

Create a VM with an alias IP range in a secondary CIDR range

Use this procedure if you want to assign an alias IP range taken from a secondary range of the subnet. Keeping the alias IP ranges separate from the primary range of the subnet makes it easier to create firewall rules that allow access to the services running on a VM, but not to the VM's primary IP address.

Console

Go to the VM instances page in the Google Cloud console.
Go to the VM instances page
Click Create instance.
Enter a Name for the new instance.
Specify a Zone.
Click Management, security, disks, networking, sole tenancy.
Click the Networking tab.
Click the edit (pencil icon) button next to the primary interface in the Network interfaces section.
Click Show alias IP ranges.
Select the Subnetwork that has the secondary range.
Under Subnet range, select the Secondary IP range you wish to use.
Enter an Alias IP range in CIDR notation. This range must be an unused range of the secondary IP range.
Click Create.

gcloud

gcloud compute instances create vm3 \
    --zone ZONE \
    --network-interface subnet=SUBNET_NAME,aliases=RANGE_NAME:RANGE_CIDR

where

ZONE is the zone that will contain the instance.
SUBNET_NAME is the name of the subnet that will contain the instance.
RANGE_NAME the name of the subnet secondary range from which to draw the alias IP range.
RANGE_CIDR is the IP range to assign to the interface. The range can be a specific range (192.168.100.0/24), a single IP address (192.168.100.1), or a net mask in CIDR format (/24). If the IP range is specified by netmask only, the IP allocator chooses an available range with the specified netmask and allocates it to the network interface.

For the complete syntax , see the gcloud documentation.

API

Create an instance with an alias IP address from the secondary IP address range of the instance's subnet.

POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances
{
  "networkInterfaces": [
    {
      "aliasIpRanges": [
        {
          "ipCidrRange": "SECONDARY_CIDR_RANGE",
          "subnetworkRangeName": "SECONDARY_RANGE_NAME"
        }
      ]
    },
    ...
  ],
  ...
}

Replace the placeholders with valid values:

PROJECT_ID is the ID of the project where you create the instance.
SECONDARY_CIDR_RANGE is the IP range to assign to the interface. The range can be a specific range (192.168.100.0/24), a single IP address (192.168.100.1), or a net mask in CIDR format (/24). If you specify the IP range by netmask only, the IP address allocator chooses an available range with the specified netmask and assigns it to the network interface.
SECONDARY_RANGE_NAME the name of the subnet secondary range from which to draw the alias IP range.
ZONE is the Google Cloud zone where the instance will be created.

For more information, see the instance.insert method.

Create a VM with multiple interfaces and alias IP addresses

This example creates two networks, each with one subnet, and a VM with interfaces in both networks. If you already have two VPC networks, you can skip to the "create VM instance" step.

Console

Create the first network and subnet:

Go to the VPC networks page in the Google Cloud console.
Go to the VPC networks page
Click Create VPC network.
Enter a Name of my-network1.
With Subnet creation mode set to Custom, specify a subnet Name of my-subnet1.
Specify a Region.
Set IP address range to 172.16.1.0/24.
Click Create secondary IP range.
Set Subnet range name torange1
Set the Secondary IP range to 10.1.0.0/16.
Click Done.
Click Create.

Create the second network and subnet:

Go to the VPC networks page in the Google Cloud console.
Go to the VPC networks page
Click Create VPC network.
Enter a Name of my-network2.
With Subnet creation mode set to Custom, specify a subnet Name of my-subnet2.
Specify the same Region as you did for the first network and subnet.
Set IP address range to 172.16.2.0/24.
Click Create secondary IP range.
Set Subnet range name torange2.
Set the Secondary IP range to 10.2.0.0/16.
Click Done.
Click Create.

Create a VM with interfaces in both networks:

Go to the VM instances page in the Google Cloud console.
Go to the VM instances page
Click Create Instance.
Set the zone to the region where you created the subnets.
Click Management, security, disks, networking, sole tenancy.
Click Networking.
Click on the first network interface.
Set Network to my-network1.
Set Subnetwork to my-subnet1.
Click Show alias IP ranges.
Click Add Alias IP range.
Set Subnet range to Primary.
Set Alias IP range to /32.
Click Add IP range.
Set Subnet range to range1.
Set Alias IP range to /24.
Click Done.
Click Add network interface.
Select my-network2.
Set Subnetwork to my-subnet2.
Click Show alias IP ranges.
Click Add Alias IP range.
Set Subnet range to Primary.
Set Alias IP range to /32.
Click Add IP range.
Set Subnet range to range2.
Enter an Alias IP range of /24.
Click Done.
Click Create.

gcloud

Create the first network:

gcloud compute networks create my-network1 --subnet-mode CUSTOM

Add a subnet:

gcloud compute networks subnets create my-subnet1 \
    --network my-network1 \
    --range 172.16.1.0/24 \
    --secondary-range range1=10.1.0.0/16

Create a second network:

gcloud compute networks create my-network2 --subnet-mode CUSTOM

Add a subnet:

gcloud compute networks subnets create my-subnet2 \
    --network my-network2 \
    --range 172.16.2.0/24 \
    --secondary-range range2=10.2.0.0/16

Create a VM with interfaces in both networks. The first network interface listed, the one in my-subnet1, is the primary interface:

gcloud compute instances create multi-nic-alias-vm \
    --machine-type f1-micro \
    --network-interface "subnet=my-subnet1,aliases=/32;range1:/24" \
    --network-interface "subnet=my-subnet2,aliases=/32;range2:/24"

Use the display command to see the interfaces and their addresses:

gcloud compute instances describe multi-nic-alias-vm

...
networkInterfaces:
- ...
  aliasIpRanges:
  - ipCidrRange: 172.16.1.2/32
  - ipCidrRange: 10.1.0.0/24
    subnetworkRangeName: range1
  name: nic0
  network: .../networks/my-network1
  networkIP: 172.16.1.3
  subnetwork: .../subnetworks/my-subnet1
  ...
- ...
  aliasIpRanges:
  - ipCidrRange: 172.16.2.2/32
  - ipCidrRange: 10.2.0.0/24
    subnetworkRangeName: range2
  name: nic1
  network: .../networks/my-network2
  networkIP: 172.16.2.3
  subnetwork: .../subnetworks/my-subnet2

API

Create two custom mode VPC networks named my-network1 and my-network2. For more information, refer to Creating a custom mode network.
Add subnets to the VPC networks. For more information, refer to Adding subnets.
1. Add a subnet named my-subnet1 to my-network1. Specify 172.16.1.0/24 for the primary range and 10.1.0.0/16 for the secondary range with the name range1.
2. Add a subnet named my-subnet2 to my-network2. Specify 172.16.2.0/24 for the primary range and 10.2.0.0/16 for the secondary range with the name range2.

Create a VM instance with interfaces in both networks.

POST https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances
{
  "networkInterfaces": [
    {
      "subnetwork": "projects/PROJECT_ID/regions/REGION/subnetworks/my-subnet1",
      "aliasIpRanges": [
        {
          "ipCidrRange": "/32",
        },
        {
          "subnetworkRangeName": "range1",
          "ipCidrRange": "/24"
        }
      ]
    },
    {
      "subnetwork": "projects/PROJECT_ID/regions/REGION/subnetworks/my-subnet2",
      "aliasIpRanges": [
        {
          "ipCidrRange": "/32",
        },
        {
          "subnetworkRangeName": "range2",
          "ipCidrRange": "/24"
        }
      ]
    }
  ],
  ...
}

Replace the placeholders with valid values:

PROJECT_ID is the ID of the project where you create the instance.
REGION is the Google Cloud region where the subnet is located. The subnets must be in the same region as the instance.
ZONE is the Google Cloud zone where the instance will be created.

For more information, see the instance.insert method.

Add alias IP ranges to an existing instance

You can add an alias IP range to a running instance.

The new addresses might not be available immediately, even after the API call has finished. They will be available only after the guest OS has added the addresses and routes.

Console

Go to the VM instances page in the Google Cloud console.
Go to the VM instances page
Click on the name of an existing instance.
Click Edit.
Click on the network interface nic0 (or the network interface to which you will add an alias IP range).
Click Show alias IP ranges.
Click Add IP range.
Select a Subnet range.
Enter an alias IP range.
Click Done.
Click Save.

gcloud

gcloud compute instances network-interfaces update INSTANCE_NAME \
    --zone ZONE \
    [--network-interface NETWORK_INTERFACE; default="nic0"]
    --aliases "RANGE_NAME_1:RANGE_CIDR_1;RANGE_NAME_2:RANGE_CIDR_2;..."

Replace the following:

ZONE is the zone that contains the instance.
NETWORK_INTERFACE is the name of the network interface to which you're adding an alias IP address range.
RANGE_NAME_1 and RANGE_NAME_2 are the names of the subnet secondary ranges from which to draw the alias IP range. If you are assigning ranges from the subnet's primary range, omit this value.
RANGE_CIDR_1 and RANGE_CIDR_2 are the IP ranges to assign to the interface. The ranges can be a specific range (192.168.100.0/24), a single IP address (192.168.100.1), or a netmask in CIDR format (/24). If the IP range is specified by netmask only, the IP allocator chooses an available range with the specified netmask and allocates it to the network interface.

For the complete syntax, see the gcloud documentation.

API

Add alias IP ranges to an existing instance.

PATCH https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances/INSTANCE_NAME/updateNetworkInterface?networkInterface=NETWORK_INTERFACE_NAME
{
  "aliasIpRanges": [
    {
      "ipCidrRange": "SECONDARY_IP_RANGE",
      "subnetworkRangeName": "SECONDARY_RANGE_NAME"
    },
    existing ranges...
  ],
  "fingerprint": "INTERFACE_FINGERPRINT"
}

Replace the placeholders with valid values:

PROJECT_ID is the ID of the project that contains the instance to modify.
INSTANCE_NAME is the name of the instance to modify.
NETWORK_INTERFACE_NAME is the name of the instance's network interface to modify.
INTERFACE_FINGERPRINT is the finger print ID for the existing network interface, which is provided when you describe an instance.
SECONDARY_CIDR_RANGE is the IP range to assign to the interface. The range can be a specific range (192.168.100.0/24), a single IP address (192.168.100.1), or a net mask in CIDR format (/24). If you specify the IP range by netmask only, the IP address allocator chooses an available range with the specified netmask and assigns it to the network interface.
SECONDARY_RANGE_NAME is the name of the subnet secondary range from which to draw the alias IP range. If you are assigning ranges from the subnet's primary range, omit this field.
ZONE is the Google Cloud zone where the instance will be created.

For more information, see the instance.updateNetworkInterface method.

Modify alias IP ranges for an existing instance

You can add more alias IP ranges to an existing instance or remove one or more ranges.

The address changes might not be visible immediately. The API call has to finish and the guest OS has to modify the addresses and routes.

Console

Go to the VM instances page in the Google Cloud console.
Go to the VM instances page
Click on the name of an existing instance.
Click Edit.
Click on the network interface nic0 (or the network interface you will modify).
Click Show alias IP ranges.
To add an alias IP range, click Add Alias IP range.
To remove an alias IP range, click on the X next to the alias IP range.
Click Done.
Click Save.

gcloud

gcloud compute instances network-interfaces update INSTANCE_NAME \
    --zone ZONE \
    [--network-interface NETWORK_INTERFACE; default="nic0"] \
    --aliases "RANGES_TO_RETAIN;NEW_RANGE_NAME:NEW_RANGE_CIDR;..."

Replace the following:

ZONE: the zone that contains the instance
NETWORK_INTERFACE: the name of the network interface that you're modifying
RANGES_TO_RETAIN: the existing ranges, in CURRENT_RANGE_NAME:CURRENT_RANGE_CIDR format, that you want to retain. If you are adding ranges to an instance that doesn't have any, these values are blank. If you are removing all ranges from the instance, the entire --aliases field is blank.
NEW_RANGE_NAME: the name of the subnet secondary range from which to draw any new alias IP ranges. If you are assigning ranges from the subnet's primary range, omit this value.
NEW_RANGE_CIDR: the IP address range to assign to the interface. This range can be a specific range (192.168.100.0/24), a single IP address (192.168.100.1), or a net mask in CIDR format (/24). If the IP address range is specified by netmask only, the IP allocator chooses an available range with the specified netmask and allocates it to the network interface.

To add ranges, run the command and specify all the existing and all the new alias IP ranges. Pairs are separated by semicolons. Example: --aliases "CURRENT_RANGE_NAME:CURRENT_RANGE_CIDR;NEW_RANGE_NAME:NEW_RANGE_CIDR"

To remove ranges, run the command and specify only the alias IP ranges you want to keep. If you are keeping ranges from a secondary range, you must specify the name of the secondary range. A CIDR range can be a specific range (192.168.100.0/24) or a single IP address (192.168.100.1). Example: --aliases "RANGE_NAME:RANGE_CIDR;RANGE_CIDR"

To remove all ranges, run the command and specify the --aliases flag, but use quotes to provide a blank input. Example: --aliases ""

You cannot add and remove ranges in the same gcloud command. To remove some ranges and add others with the Google Cloud CLI, first run the command to remove unneeded ranges, and then run it again to add needed ranges.

For the complete syntax, see the gcloud documentation.

API

For a network interface of an existing instance, add or remove alias IP address ranges.

PATCH https://compute.googleapis.com/compute/v1/projects/PROJECT_ID/zones/ZONE/instances/INSTANCE_NAME/updateNetworkInterface?networkInterface=NETWORK_INTERFACE_NAME
{
  "aliasIpRanges": [
    include new and existing ranges to add them...
    exclude existing ranges to remove them...
  ],
  "fingerprint": "INTERFACE_FINGERPRINT"
}

Replace the placeholders with valid values:

PROJECT_ID is the ID of the project that contains the instance to modify.
INSTANCE_NAME is the name of the instance to modify.
NETWORK_INTERFACE_NAME is the name of the instance's network interface to modify.
INTERFACE_FINGERPRINT is the finger print ID for the existing network interface, which is provided when you describe an instance.

For more information, see the instance.updateNetworkInterface method.

Troubleshooting

Cannot create VM instance with alias IP

Verify that the network is a VPC network. Alias IPs are not supported on legacy networks.
```
gcloud compute networks list --filter="name=NETWORK_NAME"
```
The network MODE should be "auto" or "custom".
If a subnet range name is specified, verify the following:
```
gcloud compute networks subnets describe SUBNET_NAME --region=REGION
```
- the subnet has a secondary range with the corresponding name
- the requested alias IP range is inside this secondary range or, if using netmask, is smaller than the primary range.
If subnet range name is not specified, verify that the requested alias IP range is inside the primary subnet range or, if using netmask, is smaller than the primary range.

Cannot connect to alias IP

Verify firewall rules.

List all firewall-rules:

gcloud compute firewall-rules list --format=json

Verify that traffic to and from alias IP is allowed.

Note: source service account and source tags will only expand to primary network IPs of matching instances.

If necessary, add firewall rules to allow pinging alias IP:

gcloud compute firewall-rules create FIREWALL_NAME1 \
  --network NETWORK_NAME --priority 0 --source-ranges ALIAS_IP \
  --allow icmp

gcloud compute firewall-rules create FIREWALL_NAME2 \
  --network NETWORK_NAME --priority 0 --direction out \
  --destination-ranges ALIAS_IP --allow icmp

Ensure that the VM recognizes the IP alias ranges as being local. On Linux distributions such as Debian, this can typically be done as follows.
1. Connect to the instance and run this command:
```
ip route show table local
```
  The output should contain the following:
```
local ALIAS_IP_RANGE dev eth0  proto 66  scope host
```
2. Ensure that ip_aliases = true in /etc/default/instance_configs.cfg. If you have to change this, you must also restart the guest agent:
```
systemctl restart google-guest-agent
```
3. If local route is not present, configure it using this command:
```
ip route add to local ALIAS_IP_RANGE dev eth0 proto 66
```

Auto-starting service doesn't bind to alias IP address

On supported Linux distributions, alias IP addresses are automatically set as local addresses by the preinstalled guest agent. This simplifies the set up because no OS-level configuration is needed.

However, this also means that the OS doesn't recognize the alias IP addresses as local addresses before the guest agent is running. If you have auto-starting services on your VM and they start before the guest agent, they can't bind to the alias IP addresses.

For example, an Apache HTTP server might exit with the following error:

could not bind to address ALIAS_IP:80

To solve this issue, configure your service to start after the guest agent. On distributions that use systemctl, use the following steps.

As a privileged user, run the following command to add a drop-in snippet for the service that is not working correctly—for example, an Apache HTTP Server on Debian would be apache2:
```
systemctl edit YOUR_SERVICE
```
In the text editor, add the following lines. Make sure that you add the lines above the line reading Lines below this comment will be discarded.
```
[Unit]
After=google-guest-agent.service
```

My secondary IP range is not listed

Secondary IP ranges are not listed as regular subnets. In order to show that the subnet secondary IP range has been created, use the gcloud compute networks subnets describe command.

Create a subnet.

gcloud compute networks subnets create my-subnet \
    --region us-central1 \
    --network my-network \
    --range 10.9.0.0/16 \
    --secondary-range secondaryrange1=172.16.0.0/12

Created [https://www.googleapis.com/compute/v1/projects/google.com:my-project/regions/us-central1/subnetworks/my-subnet].
NAME       REGION       NETWORK     RANGE
my-subnet  us-central1  my-network  10.9.0.0/16

List your subnets.

gcloud compute networks subnets list

NAME       REGION       NETWORK     RANGE
my-subnet  us-central1  my-network  10.9.0.0/16

Get details on a subnet to see the secondary ranges.

gcloud compute networks subnets describe my-subnet --region us-central1

...
ipCidrRange: 10.9.0.0/16
...
secondaryIpRanges:
- ipCidrRange: 172.16.0.0/12
  rangeName: secondaryrange1
...

The specified subnet secondary range does not exist

When creating a VM, if you get an error saying that the secondary range does not exist, ensure the following:

That the subnet has a secondary range with the specified name.
That you are creating your VM within the subnet that has the secondary range.

You can see this error by running the following commands:

Create a subnet with a secondary range.

gcloud compute networks subnets create my-subnet \
    --region us-central1 \
    --network my-network \
    --range 10.9.0.0/16 \
    --secondary-range secondaryrange1=172.16.0.0/12

Created [https://www.googleapis.com/compute/v1/projects/google.com:my-project/regions/us-central1/subnetworks/my-subnet].
NAME       REGION       NETWORK     RANGE
my-subnet  us-central1  my-network  10.9.0.0/16

Create an instance in another network, such as the default network, rather than in the newly created subnet.

gcloud compute instances create instance-1 \
    --zone us-central1-a \
    --network default

Created [https://www.googleapis.com/compute/v1/projects/google.com:my-project/zones/us-central1-a/instances/instance-1].
NAME        ZONE           MACHINE_TYPE   PREEMPTIBLE  INTERNAL_IP  EXTERNAL_IP    STATUS
instance-1  us-central1-a  n1-standard-1               10.128.0.2     47.82.96.9  RUNNING

Try to assign an alias IP range from the subnet created in step 1. The command will fail because the secondary range is in a different subnet than the instance.

gcloud compute instances network-interfaces update instance-1 \
    --zone us-central1-a \
    --aliases secondaryrange1:172.16.0.10/32

ERROR: (gcloud.compute.instances.network-interfaces.update) HTTPError 400: Invalid value for field 'resource.aliasIpRanges[0].subnetworkRangeName': 'secondaryrange'. The specified subnetwork secondary range does not exist.

Create another instance, this one with its interface in the subnet created in step 1.

gcloud compute instances create instance-2 \
    --zone us-central1-a \
    --network-interface subnet=my-subnet

Created [https://www.googleapis.com/compute/v1/projects/google.com:my-project/zones/us-central1-a/instances/instance-2].
NAME        ZONE           MACHINE_TYPE   PREEMPTIBLE  INTERNAL_IP  EXTERNAL_IP    STATUS
instance-2  us-central1-a  n1-standard-1               10.9.0.2     38.74.204.89  RUNNING

Add an alias IP range to the interface. This time the command succeeds because the interface and the secondary range are in the same subnet.

gcloud compute instances network-interfaces update instance-2 \
    --zone us-central1-a \
    --aliases secondaryrange1:172.16.0.10/32

Updating network interface [nic0] of instance [instance-2]...done.

Cannot add and remove secondary IP ranges in the same request

Adding and removing subnetwork secondary IP ranges in the same command is not currently supported. The gcloud commands to add and remove secondary ranges will preserve the existing ranges that are not modified.

To add and remove ranges, run the two commands separately.

gcloud compute networks subnets update SUBNET_NAME \
    --add-secondary-ranges RANGE_NAME_1=RANGE_CIDR_1,RANGE_NAME_2=RANGE_CIDR_2,...

gcloud compute networks subnets update  SUBNET_NAME \
    --remove-secondary-ranges RANGE_NAME_1,RANGE_NAME_2,...

To see more details for this command, use gcloud compute networks subnets update --help.

Cannot simultaneously add and remove alias IP ranges

Adding and removing VM alias IP ranges in the same request is currently not supported.

The gcloud command to update alias IP ranges does NOT preserve the existing ranges, so omitting a range is treated as a request to delete that range.

For example, if the current VM has alias range 10.9.27.0/24 and the new requested range is /24, running the command to request the /24 will be rejected as it is interpreted as removing 10.9.27.0/24 and adding /24. The existing range must be explicitly removed before you can add the new range.

Example:

Create alias IP range.

gcloud compute instances create vm --network-interface "subnet=s1,aliases=10.9.27.0/24"

Try to add /24 without specifying the existing range. An error results.

gcloud compute instances network-interfaces update vm --aliases "/24"
ERROR: (gcloud.compute.instances.network-interfaces.update) HTTPError 400: Invalid value for field 'resource.aliasIpRanges': ''. Cannot simultaneously add and remove alias IP ranges.

Update the VM to have no alias IP range.

gcloud compute instances network-interfaces update vm --aliases ""
Updating network interface [nic0] of instance [vm]...done.

Add the new alias IP range.

gcloud compute instances network-interfaces update vm --aliases "/24"
Updating network interface [nic0] of instance [vm]...done.

To see more details for this command, use gcloud compute instances network-interfaces update --help.

Firewall rule source tags and source service accounts

Firewall source service account and source tags only expand to primary network IPs of matching instances and do not apply to alias IPs of matching instances. So, a firewall rule based on source tags will not affect traffic from an instance alias IP address. Alias IP addresses can be added to firewall rules as source or destination ranges.

Issues with VMs with multiple interfaces and alias IP ranges

See Troubleshooting for multiple interfaces.

Enabling IP alias on Google Cloud images disables `cbr0` bridge on self-managed Kubernetes clusters

On images provided by Google, the Google guest agent creates local routes for alias IP address ranges. For self-managed Kubernetes clusters, you must configure the Google guest agent so that it does not create local routes for alias IP ranges. This step isn't required for GKE clusters because GKE disables the creation of local routes for alias IP ranges on its node images.

Symptoms:

Kubernetes Pods lose network access if the local route created by the Guest agent removes the alias IP range from the cbr0 interface.
A packet capture on the Linux bridge device (tcpdump -ni cbr arp) shows a lack of ARP responses from the cbr0 interface even though that interface is up.
Inspecting the local route table (ip route show table local) reveals that the alias IP address range is assigned to the primary network interface (for example, eth0 or ens4) instead of the container bridge interface (cbr0).

Fix:

Run the appropriate command listed in Installed packages for the guest environment to determine whether the node VM is running the Google guest agent or an older Compute Engine package.
If your node VM is not running the Google guest agent, install the guest agent or use a more recent image supplied by Google.
Configure the Google guest agent to skip creating local routes for alias IP ranges and forwarding rules.
1. Edit /etc/default/instance_configs.cfg, setting ip_forwarding=false in the [NetworkInterfaces] section. You can create the [NetworkInterfaces] section if it's not already present in the instance_configs.cfg file.
2. Do one of the following tasks:
  - Restart the node VM.
  - Restart the google-guest-agent.service service and edit the local route table.
    
    To restart the google-guest-agent.service service, run sudo systemctl restart google-guest-agent.service. Then edit the local route table to remove any entries for the alias IP address ranges. For example:
```
sudo ip route del local ALIAS_IP_RANGE dev DEVICE_IDENTIFIER
```
    Replace the following:
    - ALIAS_IP_RANGE: the alias IP address range.
    - DEVICE_IDENTIFIER: the identifier of the network interface. For example, ens4 or eth0.
For more information, see the Configuration section in the Google guest agent documentation.

What's next

Read more about instances

Configure alias IP ranges

Limitations

Subnet

VM instance

VPC network

Subnet commands

Create a subnet with one or more secondary CIDR ranges

Console

gcloud

API

Terraform

Add secondary CIDR ranges to an existing subnet

Console

gcloud

API

Remove a secondary CIDR range from a subnet

Console

gcloud

API

Work with VM instances

Create a VM with an alias IP range in the primary CIDR range

Console

gcloud

API

Create a VM with an alias IP range in a secondary CIDR range

Console

gcloud

API

Create a VM with multiple interfaces and alias IP addresses

Console

gcloud

API

Add alias IP ranges to an existing instance

Console

gcloud

API

Modify alias IP ranges for an existing instance

Console

gcloud

API

Troubleshooting

Cannot create VM instance with alias IP

Cannot connect to alias IP

Auto-starting service doesn't bind to alias IP address

My secondary IP range is not listed

The specified subnet secondary range does not exist

Cannot add and remove secondary IP ranges in the same request

Cannot simultaneously add and remove alias IP ranges

Firewall rule source tags and source service accounts

Issues with VMs with multiple interfaces and alias IP ranges

Enabling IP alias on Google Cloud images disables cbr0 bridge on self-managed Kubernetes clusters

What's next

Enabling IP alias on Google Cloud images disables `cbr0` bridge on self-managed Kubernetes clusters