VCN CIDR requirement for a database using Oracle database service for Azure
May 5, 2023 | 9 minute readOracle Database Service for Azure (ODSA) has reduced the size of the minimum private CIDR range requirement when provisioning a database service, such as Oracle Base Database service, Oracle Exadata Cloud service, or MySQL HeatWave with one or more HeatWave nodes. The new minimum CIDR range requirement for an Oracle database including Base Database and MySQL is /28 (16 IPs), and /27 (32 IPs) is the minimum CIDR range requirement of Exadata Cloud using Oracle Database service for Azure. The minimum CIDR range requirement was at /23, which is a range of 512 IPs. That limit posed a challenge for some enterprise customers to provide a range of 512 private IPs, especially when they connect all their private networks together, including private networks from other public cloud and on-premises data centers.
When you provision a database service using ODSA, the build-in automation creates an Oracle Cloud Infrastructure (OCI) virtual cloud network (VCN) and its subnets using the private CIDR range. The database service then assigns IP addresses from the subnets of the VCN. The pre-deployment process checks the requirements of the requested database shape against the network CIDR specified. If the CIDR range is insufficient for the database shape, you see an error similar to the following example:
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 shapeThis blog explains the new CIDR range requirement and how the CIDR range is used within Oracle Database Service for Azure, and how to select the appropriate space based on the service you’re provisioning.
When you specify the VCN using CIDR notation in ODSA while provisioning database, that VCN CIDR is split into two subnets. One subnet is used for client and application access, and another subnet is dedicated to backup. Each subnet has only half of the specified CIDR range. Five IP addresses per subnet are reserved by Oracle Database Service for Azure and are unavailable to the service you’re provisioning. For more information on these reserved addresses, see Are there any restrictions on using IP addresses within these subnets?
The following table shows an example of how the CIDR range for the OCI VCN is divided into two subnets and the usable IPs from each subnet:
|
VCN CIDR |
Subnet CIDR |
IPs reserved per subnet |
Usable IPs per subnet |
|
/28 |
2 x /29 |
5 |
3 (2^^3 - 5) |
|
/27 |
2 x /28 |
5 |
11 (2^^4 - 5) |
|
/26 |
2 x /27 |
5 |
27 (2^^5 - 5) |
|
/25 |
2 x /26 |
5 |
59 (2^^6 - 5) |
|
/24 |
2 x /25 |
5 |
123 (2^^7 - 5) |
|
/23 |
2 x /24 |
5 |
251 (2^^8 - 5) |
|
/22 |
2 x /23 |
5 |
507 (2^^9 - 5) |
The following table shows the type and number of Oracle databases that you can provision using different CIDR range through ODSA with the feature release of reusing OCI VCNs:
|
Database shapes |
VCN CIDR range |
||||||
|
|
/28 |
/27 |
/26 |
/25 |
/24 |
/23 |
/22 |
|
Exadata X9M (Maximum 32 nodes) |
0 |
0 |
0 |
0 |
0 |
1 |
3 |
|
Exadata X8M / X9M (Eight nodes) |
0 |
0 |
0 |
1 |
3 |
7 |
14 |
|
Exadata Base System / X8M / X9M (Minimum two 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 |
|
MySQL HeatWave single node |
1 |
5 |
13 |
29 |
61 |
125 |
253 |
The following table shows the number of IP required for different shapes of databases that provision through ODSA:
|
Database shape |
Number of IPs required per database |
|
Oracle Base Database single node |
1 |
|
Oracle Base Database two nodes |
(2 * 2 nodes) + 3 SCAN = 7 |
|
MySQL HeatWave single node |
1 |
|
Exadata Base System / X8M / X9M (Minimum two nodes) |
(4 * 2 nodes) + 3 SCAN = 11 |
|
Exadata X8M / X9M (Eight nodes) |
(4 * 8 nodes) + 3 SCAN = 35 |
|
Exadata X9M (Maximum 32 nodes) |
(4 * 32 nodes) + 3 SCAN = 131 |
Conclusion
With the new release of flexible CIDR range requirement for OCI VCN, you can choose the CIDR range between /28 and /16 for OCI VCNs and appropriately size the CIDR range, depending on the type of database, number of cluster nodes, and so on that provision using ODSA. For more details, visit Network CIDR Sizing.
To learn more about multicloud use cases using ODSA, see the following resources:
- Oracle Cloud Infrastructure and Azure Interconnect Solution Playbook Docs
- Oracle Cloud Infrastructure Blog
- Oracle and Microsoft Accelerate Enterprise Cloud Adoption
- The Oracle and Microsoft cloud Partnership Accenture Report
- Getting started with Oracle Database Service for Microsoft Azure
- Read industry analyst commentary
- Announcing Oracle Database Service for Microsoft Azure
- Oracle Database Service for Microsoft Azure technical overview
- Oracle Database Service for Azure
- Oracle and Microsoft Accelerate Enterprise Cloud Adoption
- The Oracle and Microsoft cloud Partnership Accenture Report
- Learn About Disaster Recovery in Oracle Cloud Infrastructure
- Meet Cloud’s New Power Couple: Oracle Cloud Infrastructure and Microsoft Azure
- Oracle Cloud Infrastructure and Azure Interconnect Solution Playbook Docs
- Oracle Cloud Infrastructure Blog
Niranjan Mohapatra
Senior Principal Solution Architect
Niranjan Mohapatra is a senior principal solution architect in the Oracle Cloud Infrastructure team and has over 25 years of IT experience. Niranjan is experienced with Generative AI, Multicloud, Hybrid cloud, and Private cloud. He is an Oracle-certified cloud solution architect and Oracle-certified database professional. He is experienced with on-prem data center solutions as well as public cloud solutions.
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