Update a subnet properties
Find out how to update the properties of an existing subnet
Objective
This page explains how to update the properties of an existing subnet. This can be needed if you want to comply with the prerequisites to be able to use the Public Cloud Gateway: have a gateway IP defined in your subnet.
For this example, we will use a private network and a subnet with the following properties:
- CIDR 10.1.0.0/16
- DHCP enabled with allocation pool on the global range
- No gateway IP
We will see how to update it to have a gateway IP set to 10.1.0.1 and remove that IP from the allocation pool.
Requirements
You must have created a private network and a subnet as explained in this guide.
Instructions
Using the OVHcloud Control Panel
It is currently not possible to update a subnet through this interface but you can use our Horizon interface instead (see the instructions below).
Using Horizon
Connect to Horizon & choose the region where the subnet is defined as explained in this guide.
Click on Project > Network > Networks. The page will display the list of networks available which contain an OVHcloud managed network for public connectivity (Ext-Net) as well as your network.
In that list, click on your network name ("private_network_GRA11" in this example). The network detail page is then displayed.
Click the Subnets tab: the subnets from the private network are listed.
Click on your Edit Subnet. For this guide, our target is to add a gateway IP:
- Untick the
Disable Gateway. The field Gateway IP will appear. Fill it in with an IP within your CIDR (usually the first IP of the range is used). In our case, 10.1.0.1.
- Click on
Subnet Details. Update the Allocation Pools to remove the gateway IP that you entered in the previous step. In our case, we need to update from 10.1.0.1,10.1.255.254 to 10.1.0.2,10.1.255.254
Click on Save and your subnet is updated with a gateway IP!
Using the OpenStack Command Line Interface
You need to have your CLI environment set up and your variables defined.
Run the following command (replace private_network_GRA11 by the name of your private network):
❯ openstack network show private_network_GRA11
+---------------------------+--------------------------------------+
| Field | Value |
+---------------------------+--------------------------------------+
| admin_state_up | UP |
| availability_zone_hints | |
| availability_zones | |
| created_at | 2024-01-19T10:44:33Z |
| description | |
| dns_domain | None |
| id | 6b1a7c0c-58c5-427b-a21e-ba6a1485ace7 |
| ipv4_address_scope | None |
| ipv6_address_scope | None |
| is_default | None |
| is_vlan_transparent | None |
| l2_adjacency | True |
| mtu | 1500 |
| name | private_network_GRA11 |
| port_security_enabled | True |
| project_id | REDACTED |
| provider:network_type | vrack |
| provider:physical_network | None |
| provider:segmentation_id | 1700 |
| qos_policy_id | None |
| revision_number | 3 |
| router:external | Internal |
| segments | None |
| shared | False |
| status | ACTIVE |
| subnets | 15a17e0e-6767-42ea-a345-3f65ee73b47c |
| tags | |
| tenant_id | REDACTED |
| updated_at | 2024-01-19T10:44:33Z |
+---------------------------+--------------------------------------+
In this output, the subnets line provides the UID of your subnet.
You can check your subnet detail by running the following command (update the UID according to your value!):
❯ openstack subnet show 15a17e0e-6767-42ea-a345-3f65ee73b47c
+----------------------+--------------------------------------+
| Field | Value |
+----------------------+--------------------------------------+
| allocation_pools | 10.1.0.1-10.1.255.254 |
| cidr | 10.1.0.0/16 |
| created_at | 2024-01-19T10:44:33Z |
| description | |
| dns_nameservers | 213.186.33.99 |
| dns_publish_fixed_ip | None |
| enable_dhcp | True |
| gateway_ip | None |
| host_routes | |
| id | 15a17e0e-6767-42ea-a345-3f65ee73b47c |
| ip_version | 4 |
| ipv6_address_mode | None |
| ipv6_ra_mode | None |
| name | |
| network_id | 6b1a7c0c-58c5-427b-a21e-ba6a1485ace7 |
| project_id | REDACTED |
| revision_number | 0 |
| segment_id | None |
| service_types | |
| subnetpool_id | None |
| tags | |
| updated_at | 2024-01-19T10:44:33Z |
+----------------------+--------------------------------------+
Now let's update the gateway_ip and the allocation_pool:
❯ openstack subnet set --gateway 10.1.0.1 --no-allocation-pool --allocation-pool start=10.1.0.2,end=10.1.255.254 15a17e0e-6767-42ea-a345-3f65ee73b47c
You can check that the subnet has been updated:
❯ openstack subnet show 15a17e0e-6767-42ea-a345-3f65ee73b47c
+----------------------+--------------------------------------+
| Field | Value |
+----------------------+--------------------------------------+
| allocation_pools | 10.1.0.2-10.1.255.254 |
| cidr | 10.1.0.0/16 |
| created_at | 2024-01-19T10:44:33Z |
| description | |
| dns_nameservers | 213.186.33.99 |
| dns_publish_fixed_ip | None |
| enable_dhcp | True |
| gateway_ip | 10.1.0.1 |
| host_routes | |
| id | 15a17e0e-6767-42ea-a345-3f65ee73b47c |
| ip_version | 4 |
| ipv6_address_mode | None |
| ipv6_ra_mode | None |
| name | |
| network_id | 6b1a7c0c-58c5-427b-a21e-ba6a1485ace7 |
| project_id | REDACTED |
| revision_number | 1 |
| segment_id | None |
| service_types | |
| subnetpool_id | None |
| tags | |
| updated_at | 2024-01-19T14:45:11Z |
+----------------------+--------------------------------------+
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