OpenStack Add Floating IPs

Networking (Neutron)
2026-04-17T07:12:20+00:00
Learn to allocate, associate, and manage OpenStack floating IPs using CLI commands for external network access.

OpenStack Add Floating IPs

To add a floating IP, allocate it from an external network and associate it with a running instance using the OpenStack CLI.

Prerequisites

  • OpenStack 2024.2 Dalmatian with Neutron
  • External network connected to an upstream router
  • Neutron router with an external gateway set
  • Running VM on a tenant network attached to the router

Step 1: Create the External Network

Create the external network and subnet as an admin user.

source openrc admin admin

openstack network create \
  --provider-network-type flat \
  --provider-physical-network physnet-ext \
  --external \
  --share \
  external-net

openstack subnet create \
  --network external-net \
  --subnet-range 203.0.113.0/24 \
  --allocation-pool start=203.0.113.100,end=203.0.113.200 \
  --gateway 203.0.113.1 \
  --no-dhcp \
  external-subnet

Step 2: Set the Router Gateway

Connect your tenant router to the external network.

openstack router set --external-gateway external-net my-router
openstack router show my-router -c external_gateway_info

Step 3: Allocate a Floating IP

Allocate a specific IP address from the external network pool.

openstack floating ip create --floating-ip-address 203.0.113.150 external-net

Step 4: Associate with an Instance

Associate the floating IP with a running instance.

openstack server add floating ip my-instance 203.0.113.105
openstack server show my-instance -c addresses

Step 5: Configure Security Groups

Allow inbound traffic for SSH, HTTP, and ICMP.

openstack security group rule create --protocol tcp --dst-port 22 default
openstack security group rule create --protocol tcp --dst-port 80 default
openstack security group rule create --protocol icmp default
ping 203.0.113.105
ssh ubuntu@203.0.113.105

Step 6: Disassociate and Release

Remove the floating IP from an instance and release it to the pool.

openstack server remove floating ip my-instance 203.0.113.105
openstack floating ip delete 203.0.113.105

Step 7: Move a Floating IP Between Instances

Move a floating IP instantly for failover or blue-green deployments.

openstack server remove floating ip old-instance 203.0.113.105
openstack server add floating ip new-instance 203.0.113.105

Managing Floating IP Quotas

Set quotas per project and view usage.

openstack quota set --floating-ips 10 my-project
openstack floating ip list --project my-project

Floating IPs with Port Forwarding

Forward a specific external port to an internal instance port.

openstack floating ip port forwarding create \
  --internal-ip-address 192.168.1.10 \
  --internal-protocol-port 80 \
  --external-protocol-port 8080 \
  --protocol tcp \
  <floating-ip-id>

Troubleshooting

  • Cannot ping floating IP: Check security group rules allow ICMP.
  • SSH timeout: Verify port 22 is open in security group.
  • Floating IP not reachable: Ensure router has external gateway and is ACTIVE.
  • No floating IPs available: Check allocation pool range and quotas.
  • NAT not working: Verify L3 agent is running on the network node.