High Available UDP Load balancer with HAProxy

High Available UDP Load balancer with HAProxy


Deploying a high-availability UDP load balancer using HAProxy is a critical step in ensuring the reliability and scalability of network services that rely on the UDP protocol. In this tutorial, we'll guide you through the process of setting up a high-availability UDP load balancer using HAProxy on two servers for redundancy.


Before you begin, ensure you have the following prerequisites in place:

  1. Two Linux Servers: You'll need two Linux servers for this setup. These can be virtual machines or physical servers. We'll refer to them as lb1 and lb2.
  2. HAProxy Installation: Install HAProxy on both servers. You can use your system's package manager to install it. For example, on Ubuntu, you can run:bashCopy codesudo apt-get update
    sudo apt-get install haproxy
  3. Network Configuration: Ensure that your servers can communicate with the backend servers over UDP. You may need to configure firewalls or security groups to allow UDP traffic.
  4. Backend Servers: You should have one or more backend servers that will receive UDP traffic. These can be application servers, DNS servers, or any service that uses UDP.

Step 1: Configure HAProxy on lb1

Edit the HAProxy configuration file on lb1:

sudo nano /etc/haproxy/haproxy.cfg

Here's a sample HAProxy configuration for a UDP load balancer:

    log /dev/log local0
    log /dev/log local1 notice
    chroot /var/lib/haproxy
    stats socket /run/haproxy/admin.sock mode 660 level admin
    stats timeout 30s
    user haproxy
    group haproxy

    log global
    mode    udp
    option  dontlognull
    option  redispatch
    retries 3
    timeout client 30s
    timeout connect 4s
    timeout server 30s

frontend udp_frontend
    bind *:12345
    default_backend udp_backend

backend udp_backend
    balance roundrobin
    server backend1 backend1-ip:port check
    server backend2 backend2-ip:port check
  • Replace backend1-ip:port and backend2-ip:port with the IP addresses and ports of your backend servers.
  • Adjust the bind line to specify the UDP port you want HAProxy to listen on (12345 in this example).

Save the configuration file and exit.

Step 2: Configure HAProxy on lb2

Copy the HAProxy configuration from lb1 to lb2:

scp /etc/haproxy/haproxy.cfg lb2:/etc/haproxy/haproxy.cfg

Step 3: Start HAProxy on Both Servers

Start HAProxy on both lb1 and lb2:

sudo service haproxy start

Step 4: Testing and Verification

To test your UDP load balancer, you can use tools like nc (netcat) or socat to send UDP packets to the load balancer's IP address on the specified port. Observe that the traffic is distributed evenly to the backend servers.

Example using nc:

echo -n "Hello, UDP Server!" | nc -u -w1 lb-ip-address 12345

Replace lb-ip-address with the IP address of your load balancer.

Step 5: Monitoring and Maintenance

Set up monitoring and alerting to ensure the health and performance of your HAProxy instances. Tools like HAProxy Stats provide valuable insights into load balancer performance.

Regularly update HAProxy and your operating system to patch security vulnerabilities and improve performance.


You've successfully deployed a high-availability UDP load balancer using HAProxy on two servers.

This setup provides redundancy and fault tolerance, ensuring that your UDP-based services remain available and scalable.

Be sure to monitor your load balancer's health and keep HAProxy and your operating system up to date for ongoing reliability and security.