Subnets section

Each instance must have at least one connection type. CROC Cloud Platform supports creating instances attached to a subnet and/or to a virtual switch, which is located in one Availability Zone. The features of these connections types are listed below.


  • provides L2 + L3 connectivity between instances;
  • connects to the Internet via the NAT gateway (this cannot be disabled at the moment);
  • IP addresses are automatically associated to instances according to the selected address block via DHCP protocol;
  • configuring security groups on network interfaces of instances in VPC;
  • configuring network ACLs on cross-subnets level;
  • has the IP-connectivity with other VPC subnets;
  • you can attach only one subnet to an instance;
  • you can attach a subnet to an instance only when creating an instance;
  • you can’t detach a subnet from an instance;
  • you can attach external networks to a subnet;
  • you can allocate a private IP-address of subnet’s CIDR block and associate it with a public elastic IP-address.

Virtual switch:

  • provides L2 connectivity between instances;
  • can be attached to / detached from instances without their shutting down (this must be supported by OS);
  • no connectivity with other networks;
  • no IP-address space management;
  • instances from various VPCs can be attached;
  • you can attach external networks to a subnet;
  • no firewall;
  • no Internet connection.

Creating subnets

Click некартинка_5 to create a subnet.

In the dialog window enter subnet’s IP-address. Optionally, you can supply AZ, in which you want to create a Subnet. In case you don’t supply AZ, the Cloud will choose one automatically. It is impossible to predict an AZ, which will be elected by the Cloud – consistency of choice is not guaranteed. Confirm the action to proceed.


You must specify an IP-address for a new subnet from the CIDR block range of your VPC. Subnet IP-address must be specified in CIDR notation (<subnet address>/<subnet prefix>). Subnet prefix can take values of the same range as VPC CIDR block prefix (from 16 to 28).

In the Subnets section you can see the list of instances attached to the subnet and the network ACL associated with this subnet.


Allocating private addresses

“Private addresses” tab contains the list of private addresses, allocated in this subnet.

Click некартинка_9 to add a new private address to the subnet.

There are several methods for adding public address:

  • arbitrary address – allocated automatically;
  • particular address – specified by user, must be from the Subnet’s CIDR block range.

Deleting private addresses

Click некартинка_10 to delete the selected address from a list of addresses available for subnet. Address will be deleted from the list after your confirmation.

Associating with a network ACL

Click button_1 to associate a subnet with a network ACL. In the dialog window select a network ACL with which you want to associate the subnet and confirm the action.


You can associate with network ACL no more than 200 subnets of each VPC.

Deleting a subnet

Click некартинка_11 to delete a subnet. The subnet will be deleted after your confirmation.


Before deleting the subnet please make sure that it contains no instances, private addresses or external networks. Otherwise an error message will be displayed saying the subnet is not empty.