Setup LVS (Linux Virtual Server) Load Balancer on CentOS 8 / RHEL 8

Welcome to our guide on how to install and configure LVS (Linux Virtual Server) Load balancer on CentOS 8 and RHEL 8 Linux system. Linux Virtual Server is a highly scalable and highly available server built on a cluster of real servers, with the load balancer running on the Linux operating system.

We’ll install the Linux Virtual Server package on our CentOS 8 / RHEL 8 machine then configure it as a Load balancer to the backend servers. This setup assumes you have installed a CentOS/RHEL 8 server or workstation edition.

Install Linux Virtual Server (LVS on CentOS 8 / RHEL 8

Install Linux Virtual Server (LVS on CentOS 8 / RHEL 8 by running the following commands on your Server.

$ sudo yum install ipvsadm 
Last metadata expiration check: 0:11:56 ago on Thu 05 Dec 2019 09:17:32 AM EAT.
Dependencies resolved.
===================================================================================================================================================
 Package                           Arch                             Version                              Repository                           Size
===================================================================================================================================================
Installing:
 ipvsadm                           x86_64                           1.29-8.el8                           AppStream                            57 k

Transaction Summary
===================================================================================================================================================
Install  1 Package

Total download size: 57 k
Installed size: 83 k
Is this ok [y/N]: y

Step 2: Enable IP forwarding and enable service

After the package installation, enable the service and IP forwarding in your machine.

echo 'net.ipv4.ip_forward = 1' | sudo tee -a /etc/sysctl.conf 
sudo sysctl -p 

Confirm it is turned to 1.

$ sysctl net.ipv4.ip_forward
net.ipv4.ip_forward = 1

Now start the ipvsadm service. The ipvsadm command is used to configure, maintain or inspect the virtual server table in the Linux kernel.

sudo touch /etc/sysconfig/ipvsadm 
sudo systemctl enable --now ipvsadm 

The service status should show as acitve:

$ systemctl status ipvsadm 
● ipvsadm.service - Initialise the Linux Virtual Server
   Loaded: loaded (/usr/lib/systemd/system/ipvsadm.service; enabled; vendor preset: disabled)
   Active: active (exited) since Thu 2019-12-05 09:41:56 EAT; 4s ago
  Process: 2949 ExecStart=/bin/bash -c exec /sbin/ipvsadm-restore < /etc/sysconfig/ipvsadm (code=exited, status=0/SUCCESS)
 Main PID: 2949 (code=exited, status=0/SUCCESS)

Dec 05 09:41:56 centos8.novalocal systemd[1]: Starting Initialise the Linux Virtual Server...
Dec 05 09:41:56 centos8.novalocal systemd[1]: Started Initialise the Linux Virtual Server.

Configure LVS as Load Balancer.

Now that we have installed and started the services required to manage LVS firewall. it’s time to configure LVS as a Load balancer to actual backend applications.

Start by clearing IP table rules

sudo ipvsadm -C 

Add a virtual service

Add a virtual service by using the syntax:

ipvsadm -A -t (ServiceIP:Port) -s (Distribution method)

Distribution methods supported:

• rr : Round Robin – Equal load distribution among backend servers.
• wrr: Weighted Round Robin – Round robin distribution based on real servers weight.
• lc: Least-Connection – Servers with few active jobs are prioritized for new load assignment
• wlc: Weighted Least-Connection – Assign jobs to servers with fewer jobs and relative to the real servers’ weight (Ci/Wi). This is the default distribution method.

We’ll do a configuration based on below diagram.

On LVS Server, I’ll set it to listen on 192.168.122.52 port 80.

sudo ipvsadm -A -t 192.168.122.52:80 -s wlc 

The add the add the backend servers. The syntax is:

audo ipvsadm -a -t (ServiceIP:Port) -r (BackendServerIP:Port) -m

In my case, my configurations will look similar to below:

sudo ipvsadm -a -t 192.168.122.52:80 -r 192.168.122.178:80 -m 
sudo ipvsadm -a -t 192.168.122.52:80 -r 192.168.122.6:80 -m 

List current rules:

$ sudo ipvsadm -l 
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  cent01:http wlc
  -> cent03:http                  Masq    1      0          0         
  -> cent02:http                  Masq    1      0          0      

Open http port on the firewall.

sudo firewall-cmd --add-service=http --permanent
sudo firewall-cmd --reload

If you now load the LVS server IP or domain name from the browser, you should get the page on one of the backend servers.

Reload and the backend server 2 page should show.

There you have it on how to install and configure LVS on CentOS 8 and RHEL 8 Linux system.

Also check:

How To Install and Configure HAProxy on Debian 10 (Buster)

Galera Cluster High Availability With HAProxy on Ubuntu 18.04 / CentOS 7

How to Manage HAProxy servers from a Web Interface