Create and assign a Floating IP
Floating IPs are not automatically allocated to instances by default; they need to be attached manually. A Floating IP (FIP) is an additional public IP address associated with an instance. The VM instance itself is unaware of this FIP, and it won't be visible in the network interfaces. Connectivity is achieved via NAT rules, which manage the routing from the internet to the VM and vice versa. If a VM instance is deleted, the user can reuse the floating IP by attaching it to another instance.
Create a Floating IP
- Identify the network
You have to provide the network as a parameter. Get the list of available networks using the following command:
taylor@laptop:~$ openstack network list --external | grep floating
+--------------------------------------+---------------+----------------------------------------------------------------------------+
| ID | Name | Subnets |
+--------------------------------------+---------------+----------------------------------------------------------------------------+
| a6cf8d3b-92bc-4a84-ade6-e5c6715c1797 | ext-floating1 | e49440bc-ef91-45a1-8f79-25b779ff1821 |
+--------------------------------------+---------------+----------------------------------------------------------------------------+
- Create the Floating IP
taylor@laptop:~$ openstack floating ip create ext-floating1
The output will look like this:
+---------------------+--------------------------------------+
| Field | Value |
+---------------------+--------------------------------------+
| created_at | 2021-03-17T10:00:38Z |
| description | |
| dns_domain | None |
| dns_name | None |
| fixed_ip_address | None |
| floating_ip_address | 195.15.240.213 |
| floating_network_id | a6cf8d3b-92bc-4a84-ade6-e5c6715c1797 |
| id | 8e6074e7-d581-4869-ac8c-c6207bd17299 |
| name | 195.15.240.213 |
| port_details | None |
| port_id | None |
| project_id | ac4fafd60021431585bbb23470119557 |
| qos_policy_id | None |
| revision_number | 0 |
| router_id | None |
| status | DOWN |
| subnet_id | None |
| tags | [] |
| updated_at | 2021-03-17T10:00:38Z |
+---------------------+--------------------------------------+
Your IP is 195.15.240.213 but isn't attach to any instance yet.
- Attach the Floating IP to an instance
Find the name or ID of the instance you want to assign the floating IP to
taylor@laptop:~$ openstack server list
+--------------------------------------+-------------+--------+------------------------+-----------------------------------+----------------------+
| ID | Name | Status | Networks | Image | Flavor |
+--------------------------------------+-------------+--------+------------------------+-----------------------------------+----------------------+
| 0ed1c8c1-cb48-4b37-99a4-b4b5665e056a | my-vm-name3 | ACTIVE | ext-net1=195.15.241.30 | debian-10.8.0-openstack-amd64.raw | a2-ram4-disk20-perf1 |
| 9e7b9a6d-94e8-4c53-86de-55f3d7be84a3 | my-vm-name2 | ACTIVE | mynetwork=10.10.10.137 | debian-10.8.0-openstack-amd64.raw | a2-ram4-disk20-perf1 |
| 654123e5-36fc-4194-8af8-d44ea69e9712 | my-vm-name | ACTIVE | mynetwork=10.10.10.127 | debian-10.8.0-openstack-amd64.raw | a2-ram4-disk20-perf1 |
+--------------------------------------+-------------+--------+------------------------+-----------------------------------+----------------------+
Let's assume we want to attach the FIP to my-vm-name
The Floating IPs are configured in a 1 to 1 NAT with the internal IP of the instance (in this case 10.10.10.127), it is necessary to find the ID of the port/interface corresponding to this internal IP.
To do so, run the following command :
openstack port list --server <ID or VM name>
taylor@laptop:~$ openstack port list --server my-vm-name
+--------------------------------------+------+-------------------+-----------------------------------------------------------------------------+--------+
| ID | Name | MAC Address | Fixed IP Addresses | Status |
+--------------------------------------+------+-------------------+-----------------------------------------------------------------------------+--------+
| 64b0655b-d9a7-4712-9b16-1b505b065b89 | | fa:16:3e:79:b8:3b | ip_address='10.10.10.127', subnet_id='04f0e0a0-66c6-40fb-88f5-402097c0afd0' | ACTIVE |
+--------------------------------------+------+-------------------+-----------------------------------------------------------------------------+--------+
The port ID is 64b0655b-d9a7-4712-9b16-1b505b065b89
You can now assign the floating IP to the my-vm-name port
openstack floating ip set --port <instance port ID> <floating IP>
openstack floating ip set --port 64b0655b-d9a7-4712-9b16-1b505b065b89 195.15.240.213
Important Billing Note When Creating a Router Gateway
When you create a router and set its external gateway to ext-floating1 (or any external network), an additional public IP address is automatically allocated to that router. This IP is used as the router's external interface.
Warning
Keep in mind: This extra public IP address counts as a separate Floating IP and will incur additional billing on your account.
So, if you are aiming to minimize costs, be aware that:
- Creating a router with an external gateway on
ext-floating1means one extra public IP billed, even before assigning any Floating IPs to your instances. - If you only want to assign Floating IPs to instances without extra charges, avoid creating an external gateway router unnecessarily.