Plan for IP Address Space
Use the tables in this topic to find the minimum subnet CIDR size for your Oracle Database@Azure Exadata service instance.
Note the following points when setting up networking:
- IP address ranges allocated to an Exadata VM clusters must not overlap with other CIDRs in use, as this might cause routing issues. Take cross-region routing into consideration when configuring CIDRs for Oracle Database@Azure.
- For Exadata X9M: IP addresses 100.106.0.0/16 and 100.107.0.0/16 are reserved for the interconnect, and can't be allocated to client or backup networks.
Other requirements specific to the Client Subnet and the Backup Subnet are provided in the sections for each subnet type that follow.
Client Subnet requirements
The Client Subnet has the following IP address requirements:
- 4 IP addresses are needed for each virtual machine. VM clusters have a minimum of 2 virtual machines. Therefore, a VM cluster with 2 virtual machines requires 8 IP addresses in the Client Subnet. Each additional virtual machine added to a VM cluster increases the number of IP addresses needed in the Client Subnet by 4 IPs.
- Each VM cluster requires 3 IP addresses for Single Client Access Names (SCANs), regardless of how many virtual machines are present in the VM cluster.
- 17 IP addresses are reserved for networking services in the Client Subnet, regardless of how many VM clusters are present in the Client Subnet. The 17 addresses are the following: the first 16 IP addresses, and the last IP address.
Example: IP addresses required for a Client Subnet that has 1 VM cluster with 2 virtual machines
11 IPs (VM cluster with 2 virtual machines, plus 3 SCANs) + 17 IPs (Networking) = 28 IPs.
VM cluster scenarios: CIDR size needed for the Client Subnet
The following table shows scenarios of provisioned VM clusters of differing sizes. The number of each scenario that can fit in a Client Subnet depends on the CIDR size used by the subnet. This table doesn't show all possible scenarios.
| Scenario | /27 | /26 | /25 | /24 | /23 | /22 |
|---|---|---|---|---|---|---|
| 1 VM cluster with 2 virtual machines (11 IPs + 17 Networking = 28) | 1 | 4 | 10 | 21 | 45 | 91 |
| 1 VM cluster with 3 virtual machines (15 IPs + 17 Networking = 32 | 1 | 3 | 7 | 15 | 33 | 67 |
| 1 VM cluster with 4 virtual machines (19 IPs + 17 Networking = 36) | 2 | 5 | 12 | 26 | 53 | |
| 2 VM clusters with 2 virtual machines each (22 IPs + 17 Networking = 39) | 2 | 5 | 10 | 22 | 45 | |
| 2 VM clusters with 3 virtual machines each (30 IPs + 17 Networking = 47) | 1 | 3 | 7 | 16 | 33 | |
| 2 VM clusters with 4 virtual machines each (38 IPs + 17 Networking = 55) | 1 | 2 | 6 | 13 | 26 |
Backup Subnet requirements
The Backup Subnet has the following IP address requirements:
- 3 IP addresses for each virtual machine. VM clusters have a minimum of 2 virtual machines. Therefore, a VM cluster with 2 virtual machines requires 6 IP addresses in the backup subnet. Each additional virtual machine added to a VM cluster increases the number of IP addresses needed in the Backup Subnet by 3 IPs.
- Networking services require 3 IP addresses for the Backup Subnet, regardless of how many VM clusters are present in the Backup Subnet.
Example: IP addresses required for a Backup Subnet that has 1 VM cluster with 2 virtual machines
6 IPs (VM cluster with 2 virtual machines) + 3 IPs (Networking) = 9 IPs.
VM cluster scenarios: CIDR size needed for the Backup Subnet
The following table shows scenarios of provisioned VM clusters of differing sizes. The number of each scenario that can fit in a Backup Subnet depends on the CIDR size used by the subnet. This table doesn't display all possible scenarios.
| Scenario | /28 | /27 | /26 | /25 | /24 | /23 |
|---|---|---|---|---|---|---|
| 1 VM cluster with 2 virtual machines (6 IPs + 3 Networking = 9) | 1 | 3 | 7 | 14 | 28 | 56 |
| 1 VM cluster with 3 virtual machines (9 IPs + 3 Networking = 12) | 1 | 2 | 5 | 10 | 21 | 42 |
| 1 VM cluster with 4 virtual machines (12 IPs + 3 Networking = 15) | 1 | 2 | 4 | 8 | 17 | 34 |
| 2 VM clusters with 2 virtual machines each (12 IPs + 3 Networking = 15) | 1 | 2 | 4 | 8 | 17 | 34 |
| 2 VM clusters with 3 virtual machines each (18 IPs + 3 Networking = 21) | 1 | 3 | 6 | 12 | 24 | |
| 2 VM clusters with 4 virtual machines each (24 IPs + 3 Networking = 27) | 1 | 2 | 4 | 9 | 18 |
Usable IPs for Client and Backup subnets by CIDR size
The following table shows the number of IPs available for VM clusters and SCANs for various CIDR sizes, after subtracting the IPs required by the Networking services.
Allocating a larger space for the subnet than the minimum required (for example, at least /25 instead of /27) can reduce the relative impact of those reserved addresses on the subnet's available space.
| Subnet CIDR | Reserved Networking IPs for Client Subnet | Usable IPs for Client Subnet (Virtual Machines and SCANs) | Reserved Networking IPs for Backup Subnet | Usable IPs for Backup Subnet (Virtual Machines and SCANs) |
|---|---|---|---|---|
| /28 | 17 | 0 (2^4 - 17) | 3 | 13 (2^4 - 3) |
| /27 | 17 | 15 (2^5 - 17) | 3 | 29 (2^5 - 3) |
| /26 | 17 | 47 (2^6 - 17) | 3 | 61 (2^6 - 3) |
| /25 | 17 | 111 (2^7 - 17) | 3 | 125 (2^7 - 3) |
| /24 | 17 | 239 (2^8 - 17) | 3 | 253 (2^8 - 3) |
| /23 | 17 | 495 (2^9 - 17) | 3 | 509 (2^9 - 3) |
| /22 | 17 | 1007 (2^10 - 17) | 3 | 1021 (2^10 - 3) |