How to Set Up Keepalived Dual‑Host Mode for VIP Failover

Overview

This article shows how to configure keepalived in a dual‑host (master‑master) mode to demonstrate VIP address movement between two servers.

Topology

Environment

Two servers,

ka1

and

ka2

, run keepalived. The goal is to configure two virtual routers (VRRP instances) so that each server is master for one instance and backup for the other.

Configuration on ka1

<code># yum install -y keepalived
# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   notification_email {
      [email protected]
   }
   notification_email_from [email protected]
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   router_id ka1
   vrrp_mcast_group4 224.100.100.100 
}

vrrp_instance VI_1 {
    state MASTER
    interface ens33
    virtual_router_id 66
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        172.16.0.100/24 dev ens33 label ens33:1
    }
}

vrrp_instance VI_2 {
    state BACKUP
    interface ens33
    virtual_router_id 88
    priority 80
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 654321
    }
    virtual_ipaddress {
        172.16.0.200/24 dev ens33 label ens33:2
    }
}
# cat /etc/hosts
10.0.0.125 ka1
10.0.0.126 ka2
# ssh-keygen
# ssh-copy-id 10.0.0.126
</code>

Configuration on ka2

<code># yum install -y keepalived
# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   notification_email {
      [email protected]
   }
   notification_email_from [email protected]
   smtp_server 127.0.0.1
   smtp_connect_timeout 30
   router_id ka1
   vrrp_mcast_group4 224.100.100.100 
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 66
    priority 90
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
        172.16.0.100/24 dev ens33 label ens33:1
    }
}

vrrp_instance VI_2 {
    state MASTER
    interface ens33
    virtual_router_id 88
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass 654321
    }
    virtual_ipaddress {
        172.16.0.200/24 dev ens33 label ens33:2
    }
}
# cat /etc/hosts
10.0.0.125 ka1
10.0.0.126 ka2
# ssh-keygen
# ssh-copy-id 10.0.0.125
</code>

Verification

Start keepalived on

ka1

and check the interfaces:

<code># systemctl start keepalived
# ip a
1: lo: &lt;LOOPBACK,UP,LOWER_UP&gt; ...
2: ens33: &lt;BROADCAST,MULTICAST,UP,LOWER_UP&gt; ...
    inet 10.0.0.125/24 brd 10.0.0.255 scope global ens33
    inet 172.16.0.100/24 scope global ens33:1
    inet 172.16.0.200/24 scope global secondary ens33:2
</code>

Then start keepalived on

ka2

and observe the VIP shift:

<code># systemctl start keepalived
# ip a
1: lo: &lt;LOOPBACK,UP,LOWER_UP&gt; ...
2: ens33: &lt;BROADCAST,MULTICAST,UP,LOWER_UP&gt; ...
    inet 10.0.0.126/24 brd 10.0.0.255 scope global ens33
    inet 172.16.0.200/24 scope global ens33:2
</code>

VRRP Multicast Capture

<code># tcpdump -i ens33 -nn host 224.100.100.100
17:01:51.678446 IP 10.0.0.126 > 224.100.100.100: VRRPv2, Advertisement, vrid 88, prio 100, authtype simple, intvl 1s, length 20
17:01:51.949584 IP 10.0.0.125 > 224.100.100.100: VRRPv2, Advertisement, vrid 66, prio 100, authtype simple, intvl 1s, length 20
...</code>

The output confirms that each server advertises its VRRP instance and the VIPs move according to the configured priorities.

Original article: https://www.cnblogs.com/cnblogsfc/p/14269161.html