I. build lvs cluster of DR mode
Environment: DS: 192.168.4.53 VIP: 192.168.4.100
RS: 192.168.4.51 192.168.4.52
1. Establish three experimental machines and configure ip and yum warehouses
2. Configure VIP on DR

[root@53 ~]#cp /etc/sysconfig/network-scripts/ifcfg-eth0 {,:0}
[root@53 ~]#vim /etc/sysconfig/network-scripts/ifcfg-eth0:0   ##Configure eth0:0
TYPE=Ethernet
BOOTPROTO=none
NAME=eth0:0                                                   ##This item must be modified to eth0:0
DEVICE=eth0:0                                                 ##This item must be modified to eth0:0 
ONBOOT=yes 
IPADDR=192.168.4.100                                          ##This item must be modified to eth0:0
PREFIX=24
: wq
[root@53 ~]#ifup eth0:0
[root@53 ~]#yum -y install  ipvsadm.x86_64                   ##Install cluster layout software
[root@53 ~]#ipvsadm  -A -t 192.168.4.100:80 -s rr            ##Setting clusters
[root@53 ~]#ipvsadm  -a -t 192.168.4.100:80 -r 192.168.4.51 -g ##Add server
[root@53 ~]#ipvsadm  -a -t 192.168.4.100:80 -r 192.168.4.52 -g
[root@53 ~]#ipvsadm -ln                                     ##View cluster information
[root@53 ~]#ipvsadm  -save -n > /etc/sysconfig/ipvsadm      ##Save configuration permanently

3. Deploy vip on the back segment server

[root@51 ~]#cp /etc/sysconfig/network-scripts/ifcfg-lo{,:0}
[root@51 ~]#vim /etc/sysconfig/network-scripts/ifcfg-lo:0
DEVICE=lo:0
IPADDR=192.168.4.100
NETMASK=255.255.255.255
NETWORK=192.168.4.100
BROADCAST=192.168.4.100
ONBOOT=yes
NAME=lo:0
[root@51 ~]#ifup lo:0
[root@51 ~]#sysctl -a | grep arp_ignore                   ##View options related to arpannounce
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.default.arp_ignore = 0
net.ipv4.conf.eth0.arp_ignore = 0
net.ipv4.conf.eth1.arp_ignore = 0
net.ipv4.conf.eth2.arp_ignore = 0
net.ipv4.conf.eth3.arp_ignore = 0
net.ipv4.conf.lo.arp_ignore = 1
net.ipv4.conf.virbr0.arp_ignore = 0
net.ipv4.conf.virbr0-nic.arp_ignore = 0
[root@51 ~]#echo "net.ipv4.conf.all.arp_ignore = 1" >> /etc/sysctl.conf
[root@51 ~]#echo "net.ipv4.conf.lo.arp_ignore = 1" >> /etc/sysctl.conf
[root@51 ~]#sysctl -a | grep arp_announce                    ##View options related to arpannounce
net.ipv4.conf.all.arp_announce = 2
net.ipv4.conf.default.arp_announce = 0
net.ipv4.conf.eth0.arp_announce = 0
net.ipv4.conf.eth1.arp_announce = 0
net.ipv4.conf.eth2.arp_announce = 0
net.ipv4.conf.eth3.arp_announce = 0
net.ipv4.conf.lo.arp_announce = 2
net.ipv4.conf.virbr0.arp_announce = 0
net.ipv4.conf.virbr0-nic.arp_announce = 0
[root@51 ~]#echo "net.ipv4.conf.all.arp_announce = 2" >> /etc/sysctl.conf 
[root@51 ~]#echo "net.ipv4.conf.lo.arp_ignore = 1" >> /etc/sysctl.conf
[root@51 ~]#sysctl -p                                     ##This command allows the above write to take effect

**

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II. keepalived and lvs to achieve high availability
Environment: Based on the environment of Experiment 1, the following operations are arranged: add a scheduler to achieve high availability of DS, delete the cluster setting on the original DS, and the command is ipvsadm-d-t 192.168.4.100:80
1. Add a DS with ip of 192.168.4.54
The following operations are required on both machines:
2. Install ipvsadm and keepalived.x86-64 on both dispatchers
3. Modify the configuration file

vim     /etc/keepalived/keepalived.conf 
! Configuration File for keepalived
global_defs {
   notification_email {               ##Mail configuration (keealived can realize mail alarm function)
     root@localhost                   ##Inbox
   }
   notification_email_from sally@firewall.loc   ##Mail box
   smtp_server 127.0.0.1              ##Back end mail server (this machine can only write 127.0.0.1)
   smtp_connect_timeout 30
   router_id LVS_DEVEL
   vrrp_skip_check_adv_addr
   #vrrp_strict                     ##This item requires comments, otherwise iptables will be started, causing rules to restrict access
   vrrp_garp_interval 0
   vrrp_gna_interval 0
}

vrrp_instance VI_1 {               ##vrp example
    state MASTER                   ##Divided into Master and Backup
    interface eth0                 ##Network card used
    virtual_router_id 51           ##Virtual id number
    priority 150                   ##Priority (active priority is high)
    advert_int 1          
    authentication {               ##Authentication information of two dispatchers
        auth_type PASS         
        auth_pass 1111
    }
    virtual_ipaddress {            ##Set up cluster VIP
        192.168.4.100             
    }
}
//If you want to cluster websites, just do the above. Here is the lvs rule information
virtual_server 192.168.4.100 80 {        ##Cluster configuration, 80 port for website, equivalent to ipvsadm-a setting
    delay_loop 6                     
    lb_algo rr
    lb_kind DR
    persistence_timeout 50             ##The same client accesses the same server within 50 seconds, which is conducive to performance improvement
protocol TCP

real_server 192.168.4.62 80 {       ##Server configuration in cluster
        weight 1                 
         TCP_CHECK {                 ##TCP type, there must be a space between TCP_CHECK and {, remember!!!!!!
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
    real_server 192.168.4.63 80 {
        weight 1
         TCP_CHECK {
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}
  :wq

4. Startup Test

[root@54 ~]# systemctl restart keepalived.service   
[root@54 ~]#ip a s eth0
[root@54 ~]#ipvsadm 	

5. In the client access test, it will be found that only one server will be accessed. After stopping one server, httpd will be checked to see whether the email will be received and the client access will be transferred to another server