Subnets

In Opencloud, subnets are logically isolated segments within a VPC (Virtual Private Cloud) that allow for traffic management and resource distribution. Here are the key aspects of using and configuring subnets in Open Cloud:

Resource Segmentation by Subnets:

  • Public and Private Subnets: Subnets can be divided into public (with internet access) and private (without direct internet access). This allows placing public services in internet-accessible subnets and databases and other internal services in private subnets.
  • Logical Segmentation: Subnets help organize resources within a VPC and distribute them across different availability zones for increased fault tolerance.

In the VPC Networking > Subnets view, you can define an IP subnet in the standard CIDR format and assign it a name for easy reference in the user interface. It is primarily used for connecting to the VPC, as described in the VPC Introduction section. VPC subnets are defined by the following restrictions:

  • The first four IP addresses and the last IP address in each CIDR block of the subnet are unavailable for users and cannot be assigned to an instance.
  • The second address of the subnet is reserved for the router.
  • The CIDR block of the subnet can either be identical to the CIDR block of the VPC, as in the case of a single subnet, or a subset of the CIDR block of the VPC, when there are multiple subnets. In the latter case, subnet CIDR blocks cannot overlap. The allowable block size ranges from a /28 network mask to a /16 network mask.
  • Each created subnet is automatically associated with the main VPC routing table. You can change the association. A subnet can only be associated with one routing table at a time.

To create a subnet:

  • Navigate to the "VPC Networks" > "Subnets" section.
  • In the top toolbar, click "Create."
  • In the "Create Subnet" dialog box, enter the following:

 

  • Name – the name of the subnet.
  • Description – an optional description of the subnet.
  • VPC – the VPC associated with this subnet.
  • CIDR – the subnet in CIDR format based on IP/mask.
  • Tags – optional tags can be added by selecting them from a dropdown list or creating them in this field.