Guide: Load Balancers

This guide walks through creating a private network, two web server VMs, and exposing them via an OpenStack load balancer. It covers network creation, VM provisioning, floating IP assignment, basic web server setup, and load balancer configuration and testing.

Network Setup

Create a private network

openstack network create myNet

Create a subnet

openstack subnet create mySubNet_v4 --network myNet --subnet-range 192.168.100.0/24

Create a router and connect it to the public network

openstack router create myRouter
openstack router add subnet myRouter mySubNet_v4
openstack router set myRouter --external-gateway provider_net

Example: Two Webserver as Backend for the Load Balancer

Create two identical VMs

openstack server create \
  --image ubuntu-24.04 \
  --flavor m1.small \
  --network myNet \
  --key-name myKey \
  --min 2 --max 2 \
  webserver

Assign (temporary) floating IPs to make the VMs accessible

FIP1=$(openstack floating ip create provider_net -f value -c floating_ip_address)
FIP2=$(openstack floating ip create provider_net -f value -c floating_ip_address)

openstack server add floating ip webserver-1 $FIP1
openstack server add floating ip webserver-2 $FIP2

Install a basic web server on the VMs

SSH into each VM and run:

sudo apt update && \
sudo apt -y install apache2 && \
sudo systemctl enable --now apache2 && \
echo webserver-1 | sudo tee /var/www/html/index.html

Add security rules to allow HTTP access on port 80 as described in the Security section. Test the web servers:

curl $FIP1
# Expected output: webserver-1

Integrate the Webservers with a Load Balancer

Create the load balancer

openstack loadbalancer create \
  --name myLB \
  --vip-subnet-id mySubNet_v4 \
  --provider ovn

Create a listener on port 80

openstack loadbalancer listener create \
    --name myListener \
    --protocol TCP \
    --protocol-port 80 \
    myLB

Create a pool for the listener

openstack loadbalancer pool create \
    --name myPool \
    --listener myListener \
    --protocol TCP \
    --lb-algorithm SOURCE_IP_PORT

Add Web Servers to the Pool

Get the subnet ID and VM IPs:

SUBNET_ID=$(openstack subnet list --network myNet -f value -c ID)
WEB1_IP=$(openstack server show webserver-1 -f value -c addresses | grep -o '192\.168\.100\.[0-9]\+')
WEB2_IP=$(openstack server show webserver-2 -f value -c addresses | grep -o '192\.168\.100\.[0-9]\+')

Add each VM to the pool:

openstack loadbalancer member create \

   --subnet-id $SUBNET_ID \
   --address $WEB1_IP \
   --protocol-port 80 \
   myPool

openstack loadbalancer member create \

   --subnet-id $SUBNET_ID \
   --address $WEB2_IP \
   --protocol-port 80 \
   myPool

Assign a Floating IP to the Load Balancer

Create a floating IP and associate it with the VIP of the load balancer:

FIP=$(openstack floating ip create provider_net -f value -c floating_ip_address)
VIPPORT=$(openstack loadbalancer show myLB -f value -c vip_port_id)
openstack floating ip set --port $VIPPORT $FIP

Test the load balancer:

curl $FIP

Expected output (may alternate between VMs): webserver-1 / webserver-2