准备web服务器并使用脚本绑定VIP至web服务器lo网卡

#准备两台后端RS主机
[root@rs1 ~]# cat lvs_dr_rs.sh 
#!/bin/bash
vip=10.0.0.100
mask='255.255.255.255'
dev=lo:1
rpm -q httpd $> /dev/null || yum -y install httpd &> /dev/null
service httpd start &> /dev/null && echo "The httpd Server is Ready!"
echo "<h1>`hostname`</h1>" > /var/www/html/index.html

case $1 in
start)
    echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore
    echo 1 > /proc/sys/net/ipv4/conf/lo/arp_ignore
    echo 2 > /proc/sys/net/ipv4/conf/all/arp_announce
    echo 2 > /proc/sys/net/ipv4/conf/lo/arp_announce
    ifconfig $dev $vip netmask $mask 
    echo "The RS Server is Ready!"
    ;;
stop)
    ifconfig $dev down
    echo 0 > /proc/sys/net/ipv4/conf/all/arp_ignore
    echo 0 > /proc/sys/net/ipv4/conf/lo/arp_ignore
    echo 0 > /proc/sys/net/ipv4/conf/all/arp_announce
    echo 0 > /proc/sys/net/ipv4/conf/lo/arp_announce
    echo "The RS Server is Canceled!"
    ;;
*)
    echo "Usage: $(basename $0) start|stop"
    exit 1
    ;;
esac 

[root@rs1 ~]# bash lvs_dr_rs.sh start
The httpd Server is Ready!
The RS Server is Ready!

[root@rs1 ~]# ip a 
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet 10.0.0.100/32 scope global lo:1
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether 00:0c:29:ff:d7:7d brd ff:ff:ff:ff:ff:ff
    inet 10.0.0.40/24 brd 10.0.0.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::fbf3:9a70:f1bb:88ed/64 scope link dadfailed tentative noprefixroute 
       valid_lft forever preferred_lft forever
    inet6 fe80::63d5:8547:bef8:27bc/64 scope link dadfailed tentative noprefixroute 
       valid_lft forever preferred_lft forever
    inet6 fe80::2097:51de:521a:1cdb/64 scope link dadfailed tentative noprefixroute 
       valid_lft forever preferred_lft forever
[root@rs1 ~]# 

#测试直接访问两台RS
[root@client ~]# curl 10.0.0.40
<h1>rs1.example.com</h1>
[root@client ~]# curl 10.0.0.50
<h1>rs2.example.com</h1>
[root@client ~]# 

配置keepalived

#ka1节点的配置
[root@ka1 ~]# cat /etc/keepalived/conf.d/m1.conf 
vrrp_instance m1 {
    state MASTER
    interface ens33
    virtual_router_id 66
    priority 100
    advert_int 1
    preempt_delay 10
    authentication {
        auth_type PASS
        auth_pass 123456
    }
    virtual_ipaddress {
      10.0.0.100/24 dev ens33 label ens33:1
    }
}
virtual_server 10.0.0.100 80 {
      delay_loop 3
      lb_algo rr
      lb_kind DR
      protocol TCP
      sorry_server 127.0.0.1 80
      real_server 10.0.0.40 80 {
      weight 1
      HTTP_GET {                         #应用层检测
         url {
            path /
            status_code 200
}
           connect_timeout 1
           nb_get_retry 3
           delay_before_retry 1
}
}
     real_server 10.0.0.50 80 {
         weight 1
     TCP_CHECK {                         #另一台主机使用TCP检测
         connect_timeout 5
         nb_get_retry 3
         delay_before_retry 3
         connect_port 80
}
}
}
[root@ka1 ~]# 

#ka2节点的配置，配置和ka1基本相同，只需修改

route_id ka2.example.com
state BACKUP
priority 80

访问测试结果

[root@client ~]# curl 10.0.0.100
<h1>rs2.example.com</h1>
[root@client ~]# curl 10.0.0.100
<h1>rs1.example.com</h1>

[root@ka1 ~]# yum install -y ipvsadm
[root@ka1 ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  10.0.0.100:80 rr
  -> 10.0.0.40:80                 Route   1      0          2         
  -> 10.0.0.50:80                 Route   1      0          2         
[root@ka1 ~]# 

模拟故障

#第一台rs1故障，自动切换rs2
[root@rs1 ~]# chmod 0 /var/www/html/index.html

[root@client ~]# curl 10.0.0.100 
<h1>rs2.example.com</h1>
[root@client ~]# curl 10.0.0.100 
<h1>rs2.example.com</h1>
[root@client ~]# 

[root@ka1 ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  10.0.0.100:80 rr
  -> 10.0.0.50:80                 Route   1      0          2         
[root@ka1 ~]# 

#后端rs服务器都故障，启动Sorry Server
[root@ka1 ~]# yum install -y nginx
[root@ka1 ~]# systemctl start nginx
[root@ka1 ~]# echo 'Sorry Server on ka1' > /usr/share/nginx/html/index.html 
[root@ka1 ~]# cat /usr/share/nginx/html/index.html 
Sorry Server on ka1

[root@rs2 ~]# systemctl stop httpd
[root@client ~]# curl 10.0.0.100
Sorry Server on ka1

[root@ka1 ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  10.0.0.100:80 rr
  -> 127.0.0.1:80                 Route   1      0          1         
[root@ka1 ~]# 

#ka1故障，自动切换至ka2
[root@ka1 ~]# killall keepalived
[root@client ~]# curl 10.0.0.100
Sorry Server on ka2

#恢复都有后端RS
[root@rs1 ~]# chmod 644 /var/www/html/index.html 
[root@rs2 ~]# systemctl start httpd
[root@client ~]# curl 10.0.0.100
<h1>rs2.example.com</h1>
[root@client ~]# curl 10.0.0.100
<h1>rs1.example.com</h1>

#恢复ka1服务器，又抢回原先的VIP
[root@ka1 ~]# systemctl start keepalived
[root@ka1 ~]# hostname -I
10.0.0.10 10.0.0.100 

[root@ka2 ~]# hostname -I
10.0.0.20