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      Creating a floating IP address using the OpenStack API

      • by Jason Kennedy ● August 13th, 2015

      • Tags:

        • openstack

        • floating ip address

        • api

      Today we’re going to run through the process necessary to add a floating IP address to one of your instances. I touched on how to complete this at the end of Creating Additional Networks in OpenStack via the Horizon Panel, so let’s run this example through the terminal. The first thing to consider is that creating a floating IP doesn’t actually create the address, it merely allocates one from the assigned pool. Let’s take a look at what we have assigned:

      $neutron net-list | grep external
| c3e6c57d-83fd-412e-a9f5-18ea9f566e7b | external | 5391022f-29c5-4c5b-b329-31dbfa7dece4 173.247.106.0/27 |

#neutron floatingip-create c3e6c57d-83fd-412e-a9f5-18ea9f566e7b
Created a new floatingip:
+---------------------+--------------------------------------+
| Field | Value |
+---------------------+--------------------------------------+
| fixed_ip_address | |
| floating_ip_address | 173.247.106.23 |
| floating_network_id | c3e6c57d-83fd-412e-a9f5-18ea9f566e7b |
| id | 953cda96-1a33-4645-a4e2-1b00d6e06736 |
| port_id | |
| router_id | |
| status | DOWN |
| tenant_id | 669d7a58eebb43b5b022f9d25dee47b5 |
+---------------------+--------------------------------------+

      Now that the IP has been created, we can go ahead and attach it to our instance. We’ll need the port ID of our instance’s internal IP address, and the ID of the floating IP, which we can see above.

      # nova list
+--------------------------------------+------------------------------+---------+------------+-------------+----------------------------------------+
| ID | Name | Status | Task State | Power State | Networks |
+--------------------------------------+------------------------------+---------+------------+-------------+----------------------------------------+
| ccffca1d-cb3f-4036-a450-226efd6e6eb3 | hwraid                       | ACTIVE  | -          | Running     | internal=10.230.16.131, 173.247.106.12 |
+--------------------------------------+------------------------------+---------+------------+-------------+----------------------------------------+

      So there’s our instance (pardon the formatting) and its internal IP. Let’s now use that information to find the port.

      # neutron port-list | grep 10.230.16.131
| 1a276fd5-1f88-4e5a-a9ca-b02671310c44 | | fa:16:3e:eb:fb:29 | {"subnet_id": "d813c41f-3235-4b00-a41b-1f17d4011a84", "ip_address": "10.230.16.131"} |

      So there it is! Now all we need is the floating IP’s ID. We already have that, under the floating_network_id above when we created it: 953cda96-1a33-4645-a4e2-1b00d6e06736. The final step is to associate them.

      # neutron floatingip-associate 953cda96-1a33-4645-a4e2-1b00d6e06736 1a276fd5-1f88-4e5a-a9ca-b02671310c44
Associated floatingip 953cda96-1a33-4645-a4e2-1b00d6e06736

      The command nova list should now show you both IP addresses associated with your instance:

      # nova list | grep [myinstance]
| ccffca1d-cb3f-4036-a450-226efd6e6eb3 | [myinstance]                       | ACTIVE  | -          | Running     | internal=10.230.16.131, 173.247.106.23 |

      At any point you want, you may also disassociate a floating IP by running the command followed by the ID of the address in question. We’ll disassociate the address we just assigned to our instance below.

      # neutron floatingip-disassociate 953cda96-1a33-4645-a4e2-1b00d6e06736
Disassociated floatingip 953cda96-1a33-4645-a4e2-1b00d6e06736

      You will note the address is no longer associated with your instance.

      • In OpenStack, floating IPs are publicly routable IPs that you assign to your VMs. What happens inside the VM once the floating IP is added? The answer is … nothing. If you log in via SSH and display the network configuration, you will see there is still a single network interface with a fixed IP configured. All setup is done on the compute hypervisor itself. OpenStack Neutron sets up the NAT between the VM’s fixed and floating IPs.

      One of the big advantages of floating IPs is: If a VM dies, you can re-use the floating IP by attaching it to another VM.

      For more information, please see: https://www.mirantis.com/blog/configuring-floating-ip-addresses-networking-openstack-public-private-clouds/