Assigning IP to instance¶

General concept¶

An IP address is normally assigned the instance upon creation.

This is the recommended approach to assigning an IP address (and thus, access to a network) as it will run cloud-init and (provided you’ve assigned a subnet) setup your ip-configuration for you.

This is only done on instance provisioning so any extra ports you assign, will have to be manually configured in the operating system.

Aside from the single IP that is normally setup during provisioning, two main use-cases for connecting extra IP addresses to an instance exists:

If your instances needs connect to different networks, this is possible to do when provisioning a new instance as you can add one or more ports.
If your instance needs to have extra IP addresses from the same network, this is possible when launching an instance using OpenStack Horizon or the OpenStack terminal client by first manually creating one or more ports and assigning them.

More information on the concepts of networking in our networking section.

Tip

Adding an extra IP address by using the platform is analogous to adding a port and connecting it to the instance.

You need to add more ports to your instance to access more then one network, if the network is already connected through an existing port you can use that.

Assigning an IP after instance creation¶

To add an IP after creating your instance, the process consists of either creating a port and then assigning it to an instance or, as the below guide will detail, connecting an instance to a network (and by doing so, creating a port in the process).

Important

When adding more ports to your instances, its possible that your instance might loose its network connectivity when taking the IP configuration live in the operating system.

Its also possible that floating IP addresses might need to be re-assigned to the new port depending on if the default route on the instance changes. We recommend doing changes to interfaces network configuration during a maintenance window.

Note

Below is an example on how to add networks which will add a port automatically. If you prefer to create the ports yourself (more information in the Ports article), another option is to assign an already created port.

Assigning a port using the cloud management portal¶

To assign a port to an instance by using the Cloud management portal

Press Compute and then Instances in the sidebar menu.
Press the instance you want to assign the port to.
Press the Network tab.
Press the Add port button.
Choose the network and subnet you want to connect to.
Press Add port

Your port might not be active in your operating system until it’s configured there.

Assigning a port using the OpenStack Horizon portal¶

To assign a port to an instance by using OpenStack Horizon

Under Project, click Compute and then Instances in the sidebar menu.
In the dropdown menu to the far right of the line corresponding to the instance you want to resize, press Attach Interface
Under Network, select the network (it will also show subnets) you want to connect to.
Press Attach interface

Your port might not be active in your operating system until it’s configured there.

Assigning a port using the OpenStack terminal client¶

To assign a port to an instance by using the OpenStack Terminal Client

Run this command: openstack server list. Save the name of the instance you want to assign the port to.
Run this command: openstack network list. Save the name of the network you want to connect to the instance.
Run this command: openstack server add fixed ip [SERVER NAME] [NETWORK NAME], replacing the values in angle brackets by the information from the previous steps.

Your port might not be active in your operating system until it’s configured there.

Note

If you remove an existing port and add a new one, you might have problems with udev persistent rules because of new MAC address depending on the operating system.

We would recommend making sure that you have console access to your instance and a password to login with when changing networking.