Step-by-Step Guide to Building an LVS+Keepalived High Availability Cluster with Nginx

This article provides a detailed, step‑by‑step tutorial for building a high‑availability load‑balancing cluster using LVS (IPVS) and Keepalived on four CentOS 7 servers, with Nginx as the web server.

Preparation : Four servers with IPs 192.168.210.85, 192.168.210.177, 192.168.210.8, and 192.168.210.195 are designated. System services include LVS and Keepalived; the web server runs Nginx, and the cluster uses the LVS DR mode.

Installation of required packages is performed with yum:

yum install ipvsadm -y

yum install keepalived -y

After installation, the Keepalived configuration file is edited (e.g., /etc/keepalived/keepalived.conf ) with the following content:

global_defs {
    notification_email {
        [email protected]
    }
    lvs_id hahashen1
}

vrrp_instance LVS {
    state MASTER
    interface ens33
    virtual_router_id 51
    priority 200
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 1111
    }
    virtual_ipaddress {
        192.168.210.11
    }
}

virtual_server 192.168.210.11 80 {
    delay_loop 1
    lb_algo rr
    lb_kind DR
    persistence_time 0
    protocol TCP
    real_server 192.168.210.84 80 {
        weight 1
        TCP_CHECK {
            connection_timeout 10
            nb_get_retry 3
            delay_before_retry 3
        }
    }
    real_server 192.168.210.195 80 {
        weight 1
        TCP_CHECK {
            connection_timeout 10
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}

The Keepalived service is then started:

systemctl start keepalived

Nginx installation on the two web servers (192.168.210.84 and 192.168.210.195) is done with:

yum install nginx -y

A helper script ( lvsnginx.sh ) configures the virtual IP and necessary kernel parameters:

#!/bin/bash
ifconfig lo:0 192.168.210.11 netmask 255.255.255.255 broadcast 192.168.210.11 up
route add -host 192.168.210.11 dev lo:0
echo "0" > /proc/sys/net/ipv4/ip_forward
echo "1" > /proc/sys/net/ipv4/conf/lo/arp_ignore
echo "2" > /proc/sys/net/ipv4/conf/lo/arp_announce
echo "1" > /proc/sys/net/ipv4/conf/all/arp_ignore
echo "2" > /proc/sys/net/ipv4/conf/all/arp_announce
exit 0

After deploying the script and starting Keepalived, the setup is verified using ipvsadm -ln , which should display the virtual server 192.168.210.11:80 with two real servers (192.168.210.84 and 192.168.210.195) in the routing table.

This concludes the configuration, providing a functional LVS+Keepalived load‑balancing cluster with Nginx.