Overview of VCNs and Subnets

Next you'll typically want to create one or more subnets in the cloud network.

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Click the VCN you're interested in.
3. Click Create Subnet.

4. In the Create Subnet dialog box, you specify the resources to associate with the subnet (for example, a route table). By default, the subnet is created in the current compartment, and you choose the resources from the same compartment. Click the click here link in the dialog box if you want to enable compartment selection for the subnet and each of those resources.

   Enter the following:

   • Create in Compartment: If you've enabled compartment selection, specify the compartment where you want to put the subnet.
   • Name: A friendly name for the subnet. It doesn't have to be unique, and it cannot be changed later in the Console (but you can change it with the API). Avoid entering confidential information.
   • Regional or AD-specific subnet: Oracle recommends creating only regional subnets, which means that the subnet can contain resources in any of the region's availability domains. If you instead choose Availability Domain-Specific (the only type of subnet that Oracle originally offered), you must also specify an availability domain. This choice means that any instances or other resources later created in this subnet must also be in that availability domain.
   • IPv4 CIDR Block: A single, contiguous CIDR block for the subnet (for example, 172.16.0.0/24). Ensure that it's within the cloud network's CIDR block and doesn't overlap with any other subnets. You can change the size of this CIDR block later. See Allowed VCN Size and Address Ranges. For reference, here's a CIDR calculator.
   • IPv6 Prefixes: You can request an Oracle-allocated IPv6 /64 prefix, or enter BYOIPv6 or ULA prefixes. You can have a maximum of three IPv6 prefixes in a subnet. Once you have assigned an IPv6 prefix to a VCN, it must always have at least one IPv6 prefix assigned to it. This option is available for VCNs in all commercial and government regions, provided the VCN is already enabled for IPv6. For more information, see IPv6 Addresses.
   • Route Table: The route table to associate with the subnet. If you've enabled compartment selection, under Route Table Compartment, you must specify the compartment that contains the route table.
   • Private or public subnet: This controls whether VNICs in the subnet can have public IP addresses. For more information, see Access to the Internet.
   • Use DNS Hostnames in this Subnet: This option is available only if you provided a DNS label for the VCN during creation. The option is required for assignment of DNS hostnames to hosts in the subnet, and also when you plan to use the VCN's default DNS feature (called the Internet and VCN Resolver). If the check box is selected, you can specify a DNS label for the subnet, or let the Console generate one for you. The dialog box automatically displays the corresponding DNS Domain Name for the subnet (<subnet_DNS_label>.<VCN_DNS_label>.oraclevcn.com). For more information, see DNS in Your Virtual Cloud Network.
   • DHCP Options: The set of DHCP options to associate with the subnet. If you've enabled compartment selection, under DHCP Options Compartment, you must specify the compartment that contains the set of DHCP options.
   • Security Lists: One or more security lists to associate with the subnet. If you've enabled compartment selection, you must specify the compartment that contains the security list.
   • Tags: If you have permissions to create a resource, then you also have permissions to apply free-form tags to that resource. To apply a defined tag, you must have permissions to use the tag namespace. For more information about tagging, see Resource Tags. If you are not sure whether to apply tags, skip this option (you can apply tags later) or ask your administrator.
5. Click Create. The subnet is then created and displayed on the Subnets page in the compartment you chose.

You can change these characteristics of a subnet:

• Name
• Size of the CIDR block
  Note
  
  

  • The CIDR block IP range you specify must be completely within one of the VCN's CIDR block ranges.
  • The new range must use the same network address as the previous range. For example, the previous and new ranges could be 10.0.0.0/25 and 10.0.0.0/24.
  • If you are reducing the CIDR range, ensure that no IP addresses outside of the reduced range are in use.
  • The new CIDR range's broadcast address (last IP address of CIDR range) must not be an IP address in use in the previous CIDR range.
  • You cannot create VNICs or private IPs for this subnet while a CIDR block update is in progress.
  • After the CIDR block update is complete, the DHCP lease for each host within the subnet must be renewed. Renewal happens automatically within 24 hours. To renew the lease immediately, refer to the applicable operating system documentation for guidance on how to renew the lease manually.
  • Ensure that you adjust your secondary VNICs and secondary IPs as applicable to match your updated VCN configuration.
  • Once you have assigned an IPv6 prefix to a VCN, it must always have at least one IPv6 prefix assigned to it.
• Which set of DHCP options the subnet uses
• Which route table the subnet uses
• Which security lists the subnet uses

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Click the VCN you're interested in.
3. Click Subnets.
4. Click the subnet you're interested in.
5. Click Edit.
6. Make your changes. Avoid entering confidential information.

7. Click Save Changes.

   The changes take effect within a few seconds.

Prerequisite: The subnet must have no instances, load balancer, OCI database systems, and orphaned mount targets in it. For more information, see Subnet or VCN Deletion.

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Click the VCN you're interested in.
3. Click Subnets.
4. Click the subnet you're interested in.
5. Click Terminate.
6. Confirm when prompted.

If the subnet is empty, its state changes to TERMINATING briefly and then TERMINATED. If the subnet is not empty, you get an error indicating that there are still instances or other resources in it that you must delete first.

Be aware of the following limitations:

• The IPv4 CIDR block or IPv6 prefix you add must not overlap with any other address range in the VCN or in a peered VCN.
• The new IPv4 CIDR block or IPv6 prefix must not include an IP address used in an existing route rule.
• You cannot create or update the VCN's subnets, VLANs, LPGs, or route tables while this VCN update is in progress.
• You cannot edit IPv6 prefixes after they are assigned to the VCN.

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Click the VCN you're interested in.
3. Click CIDR Blocks/Prefixes.
4. Click Add CIDR Block/IPv6 Prefix.
5. Enter the value of the CIDR block you want to add to the VCN.

   You can indicate you want an Oracle-allocated IPv6 prefix, specify a ULA, or select a BYOIPv6 prefix you have already imported. For BYOIPv6, you can also subdivide the prefix here, if you're only assigning a portion of the imported prefix to the VCN.

6. Click Add CIDR Block.

   The VCN's state changes to UPDATING. The time to completion can take a few minutes. You can view work requests to monitor the status of the update.

• The CIDR block range you specify must not overlap with any other CIDR block in this VCN or in a peered VCN.
• You cannot change the CIDR block to a range that excludes an IP address in use in the current CIDR block range.
• You cannot create or update the VCN's subnets, VLANs, LPGs, or route tables while this VCN update is in progress.

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Click the VCN you're interested in.
3. Click CIDR Blocks.
4. Find the CIDR block in the list, click the Actions menu, and then click Edit CIDR Block.
5. Make the applicable change.

6. Click Save Changes.

   The VCN's state changes to UPDATING. The time to completion can vary depending on the size of your network. Updating a small network could take about a minute, and updating a large network could take up to an hour. You can view work requests to monitor the status of the update.

Be aware of the following restrictions:

• You cannot remove an IPv4 CIDR block if an IP address in that range is in use.
• You cannot create or update the VCN's subnets, VLANs, LPGs, or route tables while this VCN update is in progress.
• Once you have assigned an IPv6 prefix to a VCN, it must always have at least one IPv6 prefix assigned to it.

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Click the VCN you're interested in.
3. Click CIDR Blocks.
4. Find the CIDR block in the list, click the Actions menu, and then click Remove CIDR Block.

5. Click Remove CIDR Block.

   The VCN's state changes to UPDATING. The time to completion can vary depending on the size of your network. Updating a small network could take about a minute, and updating a large network could take up to an hour. You can view work requests to monitor the status of the update.

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Click the name of the VCN that you want to delete.

3. Click Delete.

   In the Delete Virtual Cloud Network dialog box, you can select from the following options:

   • Search compartments for resources associated with this VCN: (Optional) When you select this option the process scans for active resources in the VCN. If the process finds any active resources (subnets and route tables, for example) it deletes them if possible, then deletes the VCN. If the process finds a VNIC on a compute instance, a load balancer, a database system, or a mount target, manually delete those resources and then restart the process. Oracle recommends leaving this option selected unless you’re certain the VCN and its subnets are already empty. If you select this option, you can also choose which compartments to search:
     • All (number) compartments: This option searches all compartments in the same region as this VCN for resources associated with the VCN.
     • Specific compartments: This option lets you choose specific compartments and searches only the chosen compartments for resources associated with the VCN.

     Searching more compartments takes more time, but is more thorough and has a smaller chance of failure.

4. Click Scan.

   The scan begins. Progress is displayed in the completion bar when the process identifies associated resources. The scan lists associated VCN resource types like subnets, DRG attachments, internet or NAT gateways, and so on. The process deletes associated resources in the order shown.

5. Click Delete All to delete associated resources in the order listed.

   If you don't have the needed permissions to delete an associated resource or an error occurs, the deletion process stops. Deleted VCN resources are irretrievable. Resolve the error and restart the process to delete the VCN.

   If a subnet still contains compute instances, load balancers, and so on, deleting the subnet fails. The resulting error message displays the OCID of the subnet and the blocking item in that subnet. Click on the OCID to go to the details page for that item and either delete it or move it to a subnet in a different VCN.

6. Click Close when the deletion of the VCN and all associated resources finishes.

If the VCN is empty, its state changes to TERMINATING and then TERMINATED temporarily until the VCN is completely removed. Once a deleted VCN is completely removed it no longer appears in a list of VCNs in your tenancy.

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Click the VCN you're interested in.
3. Click the Tags tab to view or edit the existing tags. Or click Apply tag(s) to add new ones.

For more information, see Resource Tags.

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Click the VCN you're interested in.
3. Click the subnet you're interested in.
4. Click the Tags tab to view or edit the existing tags. Or click Apply tag(s) to add new ones.

For more information, see Resource Tags.

You can move a VCN from one compartment to another. When you move a VCN, its associated VNICs, private IPs, and ephemeral IPs move with it to the new compartment. For more information, see To move a resource to a different compartment.

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Find the VCN in the list, click the Actions menu, and then click Move Resource.
3. Choose the destination compartment from the list.
4. Click Move Resource.
5. If there are alarms monitoring the VCN, update the alarms to reference the new compartment. See Updating an Alarm After Moving a Resource for more information.

You can move a subnet from one compartment to another. For more information, see Working with Compartments.

1. Open the navigation menu, click Networking, and then click Virtual Cloud Networks.
2. Click the VCN you're interested in.
3. Find the subnet in the list, click the Actions menu, and then click Move Resource.
4. Choose the destination compartment from the list.
5. Click Move Resource.