Subnets

A subnet is a range of private IP addresses within a Virtual Private Cloud (VPC). Subnets provide the IP addressing scheme for resources in your VPC, enabling VM-to-VM communication within the same network.

Default subnet configuration

Each VPC in evroc has one subnet per availability zone. These subnets are created automatically and each has its own IP address range:

ZoneSubnetCIDR
se-sto-adefault-se-sto-a10.0.1.0/24
se-sto-bdefault-se-sto-b10.0.2.0/24
se-sto-cdefault-se-sto-c10.0.3.0/24

Each subnet provides 252 usable private IPv4 addresses for VMs (4 addresses are reserved for the network address, default gateway, broadcast address, and one additional system address).

When you create a VM, it is automatically assigned an available private IP address from the subnet in its zone. You can't specify a particular private IP address when creating a VM—addresses are assigned automatically by the system.

Zonal scope

Subnets are zonal resources—each subnet exists in a specific availability zone. When you create a VM, it is placed in a subnet based on the zone you specify.

VMs in different subnets (and therefore different zones) can still communicate with each other over the VPC's private network, subject to security group rules. The VPC spans all zones, providing connectivity across the entire region.

Subnet properties

Each default subnet has the following characteristics:

  • IP range: /24 CIDR block (252 usable addresses for VMs)
  • Address type: Private IPv4
  • Assignment: Automatic when creating VMs (can't be manually specified)
  • Persistence: IP addresses remain associated with VMs for their lifetime

Private vs public networking

Private IP addresses in the subnet are used for internal communication between VMs within the VPC. To enable inbound access from the public internet to a VM, you must attach a Public IP to that VM in addition to its private subnet address.

All VMs have a private IP from their zone's subnet. Public IPs are optional and are only required for inbound internet connectivity.

Next steps