Network CIDR Sizing
When you provision an Oracle Base Database, an Oracle Exadata VM Cluster, or a Oracle HeatWave with one or more HeatWave nodes, you specify an network address using CIDR notation, which is a range of networking addresses the service uses. Additionally, when you provision an Oracle Exadata System, which includes VMs and database nodes within it, you also specify a network address range with CIDR. This document explains how those CIDR ranges are used within Oracle Database Service for Azure, and how to select the appropriate space based on the service you are provisioning.
Oracle Autonomous Database Serverless (ADB-S) uses a different model for networking management, and is not impacted by these requirements.
When you specify the virtual cloud network (VCN) using CIDR notation, that is split into two subnets. Each subnet has only half of the specified CIDR range. Additionally, 5 IP addresses per subnet are reserved by Oracle Database Service for Azure, and are unavailable to the service you are provisioning. For more information on these reserved addresses, see Are there any restrictions on using IP addresses within these subnets?
Table 1-2 Number of available IPs per subnet
| VCN CIDR | Subnet CIDR | IPs Reserved Per Subnet | IPs Available Per Subnet |
|---|---|---|---|
| /28 | /29 | 5 | 3 (2^3 - 5) |
| /27 | /28 | 5 | 11 (2^4 - 5) |
| /26 | /27 | 5 | 27 (2^5 - 5) |
| /25 | /26 | 5 | 59 (2^6 - 5) |
| /24 | /25 | 5 | 123 (2^7 - 5) |
| /23 | /24 | 5 | 251 (2^8 - 5) |
| /22 | /23 | 5 | 507 (2^9 - 5) |
This table helps you select an appropriate CIDR range for the specific service or services your VCN will support.
Table 1-3 Number of database systems or VM clusters supported
| Selected CIDR Range | |||||||
|---|---|---|---|---|---|---|---|
| Shape | /28 | /27 | /26 | /25 | /24 | /23 | /22 |
| Exadata X9M (max. 32 Nodes) | 0 | 0 | 0 | 0 | 0 | 1 | 3 |
| Exadata X8M / X9M (8 Nodes) | 0 | 0 | 0 | 1 | 3 | 7 | 14 |
| Exadata Base System / X8M / X9M (min. 2 Nodes) | 0 | 1 | 2 | 5 | 11 | 22 | 46 |
| Oracle Base Database Two Nodes | 0 | 1 | 3 | 8 | 17 | 35 | 72 |
| Oracle Base Database Single Node | 3 | 11 | 27 | 59 | 123 | 251 | 507 |
| Oracle HeatWave Single Node | 1 | 5 | 13 | 29 | 61 | 125 | 253 |
Reserved = 5 // Azure reserves the first 4 IPs and last IP in the CIDR range
UsedIps = Number of IPs already in use in the subnet // Zero when creating a new McVCN
if ( (CidrSize - Reserved - UsedIps) < RequiredIps )
Error: CIDR size is insufficient to support the requested DB shapeIf this happens, you will need to increase the size of the VCN for you requested shape.
Use the following table to compute the IP address requirements for your database shape.
Table 1-4 IPs required per database instance by shape
| Database Shape | Number of IPs Required per Instance |
|---|---|
| Oracle Base Database Single Node | 1 |
| Oracle Base Database Two Node | (2 * 2 nodes) + 3 SCAN = 7 |
| Oracle HeatWave Single Node | 2 |
| Exadata Base System / X8M / X9M (min. 2 Nodes) | (4 * 2 nodes) + 3 SCAN = 11 |
| Exadata X8M / X9M (8 Nodes) | (4 * 8 nodes) + 3 SCAN = 35 |
| Exadata X9M (max. 32 Nodes) | (4 * 32 nodes) + 3 SCAN = 131 |