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

# 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

Configuration on ka2

# 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

Verification

Start keepalived on ka1 and check the interfaces:

# systemctl start keepalived
# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> ...
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> ...
    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

Then start keepalived on ka2 and observe the VIP shift:

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

VRRP Multicast Capture

# 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
...

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