How to Launch an OpenStack Instance and Configure Floating IPs Step‑by‑Step

SSH public key injection

To start an instance in OpenStack you first need a VM flavor; a small‑memory flavor (e.g., m1.cirros) is created for testing.

List available images and networks:

Get all image files and network lists (illustrated in the accompanying screenshots).

Launch the instance

# nova boot --flavor m1.cirros --image cirros-0.3.4-x86_64 --nic net-id=a71cc567-08ad-4000-b273-e1b300fa642b \
    --security-group default --key-name demokey demo-i1

After booting, view the instance and open the console. The VM initially has no IP, so manual configuration is performed.

Network connectivity test

Ping the internal gateway, the virtual external gateway, and a real external gateway to verify network paths.

The tests show that the VM can reach external gateways, but external hosts cannot reach the VM, indicating the need for a floating IP.

Floating IP concept

A floating IP creates a virtual router in a network namespace; its external interface bridges to a physical network, while the internal interface connects to VMs. The external interface gets an IP address, and DNAT forwards traffic to a specific VM, while SNAT handles outbound traffic.

Create and bind a floating IP

On the controller node, allocate a floating IP (see image) and bind it to the target instance (see image).

Adjust the default security policy accordingly (see image).

After these steps, external hosts can access the VM via 172.16.20.13 (illustrated in the screenshot). The actual response originates from 192.168.22.2, but packet capture is omitted.

To SSH into the VM using the floating IP, run the appropriate SSH command (shown in the image).

With these configurations, the private cloud is essentially operational; the next component to explore would be Cinder, the storage service.