Master‑Backup High Availability with Keepalived: Step‑by‑Step Guide

Preface

In previous sections we covered Keepalived overview, principles, and detailed config file analysis; now we use several configuration examples to help you master Keepalived high availability.

Single‑Instance Master‑Backup Mode

Configure Keepalived to achieve automatic IP failover for a single instance.

1. Prepare two machines

2. Install Keepalived

yum -y install keepalived

Install on both qll251 and qll252.

3. Modify configuration file

3.1 qll251 as MASTER

vim /etc/keepalived/keepalived.conf

Instance VI_1 on qll251 is MASTER, ID 60, priority 150, floating IP 10.43.187.201.

Only note: server qll251 is master for instance VI_1 with ID 60, priority 150, floating IP 10.43.187.201.

3.2 qll252 as BACKUP

vim /etc/keepalived/keepalived.conf

4. Start Keepalived service

systemctl start keepalived

Both MASTER and BACKUP nodes must start the service.

5. Verify VIP automatic failover

Because qll251 priority > qll252, qll251 becomes MASTER and holds VIP 10.43.187.201.

qll252 as BACKUP has no floating IP.

High‑availability switch experiment

(1) Stop Keepalived on qll251 to simulate MASTER failure.

(2) Backup node takes over the VIP.

(3) Check logs for master‑backup transition.

Logs show backup node qll252 has taken over VIP 10.43.187.201, sending ARP broadcasts so clients update their ARP tables.

When the original master is restarted, it re‑claims the VIP because its priority is higher.

Result: single‑instance Keepalived provides IP automatic failover.

Dual‑Instance Dual‑Master Mode

In this mode, business A is master on qll251 and backup on qll252, while business B is opposite.

1. Prepare two machines

IP and VIP planning diagram:

2. Install Keepalived

yum -y install keepalived

Install on both servers.

3. Modify configuration files

3.1 qll251 configuration

[root@qll251 ~]# vim /etc/keepalived/keepalived.conf<br/>14     state MASTER<br/>15     interface eth0<br/>16     virtual_router_id 60<br/>17     priority 150<br/>18     advert_int 1<br/>19     authentication {<br/>20         auth_type PASS<br/>21         auth_pass 1111<br/>22     }<br/>23     virtual_ipaddress {<br/>24         10.43.187.201/24 dev eth0 label eth0:1<br/>25     }<br/>26 }<br/>27<br/>28 vrrp_instance VI_2 {<br/>29     state BACKUP<br/>30     interface eth0<br/>31     virtual_router_id 61<br/>32     priority 100<br/>33     advert_int 1<br/>34     authentication {<br/>35         auth_type PASS<br/>36         auth_pass 1111<br/>37     }<br/>38     virtual_ipaddress {<br/>39         10.43.187.202/24 dev eth0 label eth0:2<br/>40     }<br/>41 }

Instance VI_1 is master on qll251, VI_2 is backup.

3.2 qll252 configuration

[root@qll252 ~]# vim /etc/keepalived/keepalived.conf<br/>14     state BACKUP<br/>15     interface eth0<br/>16     virtual_router_id 60<br/>17     priority 100<br/>18     advert_int 1<br/>19     authentication {<br/>20         auth_type PASS<br/>21         auth_pass 1111<br/>22     }<br/>23     virtual_ipaddress {<br/>24         10.43.187.201/24 dev eth0 label eth0:1<br/>25     }<br/>26 }<br/>27<br/>28 vrrp_instance VI_2 {<br/>29     state MASTER<br/>30     interface eth0<br/>31     virtual_router_id 61<br/>32     priority 150<br/>33     advert_int 1<br/>34     authentication {<br/>35         auth_type PASS<br/>36         auth_pass 1111<br/>37     }<br/>38     virtual_ipaddress {<br/>39         10.43.187.202/24 dev eth0 label eth0:2<br/>40     }<br/>41 }

Instance VI_1 is backup, VI_2 is master on qll252.

The key differences are the state and priority values.

4. Verification

Stop Keepalived on both nodes, then start them sequentially and check IP bindings.

// On qll251<br/>systemctl start keepalived<br/>ip a | egrep "10.43.187.201|10.43.187.202"<br/># shows 10.43.187.201 and 10.43.187.202 on eth0:1 and eth0:2<br>// On qll252<br/>systemctl start keepalived<br/>ip a | egrep "10.43.187.201|10.43.187.202"<br/># shows 10.43.187.202 only<br/>

When either node fails, the VIPs switch to the other node, enabling separate services (e.g., www.cloud.com on 10.43.187.201, bbs.cloud.com on 10.43.187.202).

Conclusion

If you found this guide useful, please like or share.