keepalived高可用

Posted 2021-06-29 rmㅤ-rf *

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keepalived

keepalived是什么？

Keepalived 软件起初是专为LVS负载均衡软件设计的，用来管理并监控LVS集群系统中各个服务节点的状态，后来又加入了可以实现高可用的VRRP功能。因此，Keepalived除了能够管理LVS软件外，还可以作为其他服务（例如：nginx、Haproxy、mysql等）的高可用解决方案软件。
Keepalived软件主要是通过VRRP协议实现高可用功能的。VRRP是Virtual Router RedundancyProtocol(虚拟路由器冗余协议）的缩写，VRRP出现的目的就是为了解决静态路由单点故障问题的，它能够保证当个别节点宕机时，整个网络可以不间断地运行。
所以，Keepalived 一方面具有配置管理LVS的功能，同时还具有对LVS下面节点进行健康检查的功能，另一方面也可实现系统网络服务的高可用功能。

keepalived的重要功能

管理LVS负载均衡软件
实现LVS集群节点的健康检查
作为系统网络服务的高可用性(failover)

keepalived高可用故障转移的原理

Keepalived 高可用服务之间的故障切换转移，是通过 VRRP (Virtual Router Redundancy Protocol ,虚拟路由器冗余协议）来实现的。
在 Keepalived 服务正常工作时，主 Master 节点会不断地向备节点发送（多播的方式）心跳消息，用以告诉备 Backup 节点自己还活看，当主 Master 节点发生故障时，就无法发送心跳消息，备节点也就因此无法继续检测到来自主 Master 节点的心跳了，于是调用自身的接管程序，接管主 Master 节点的 IP 资源及服务。而当主 Master 节点恢复时，备 Backup 节点又会释放主节点故障时自身接管的IP资源及服务，恢复到原来的备用角色。
那么，什么是VRRP呢？
VRRP ,全称 Virtual Router Redundancy Protocol ,中文名为虚拟路由冗余协议，VRRP的出现就是为了解决静态踣甶的单点故障问题，VRRP是通过一种竞选机制来将路由的任务交给某台VRRP路由器的。

keepalived原理

keepalived高可用架构图

在这里插入图片描述

keepalived工作原理描述

keepalived高可用之间是通过VRRP通信的，因此，我们先了解VRRP：

VRRP，全称Virtual Router Redundant Protocol（虚拟路由冗余协议），VRRP的出现时为了解决静态路由的单点故障。
VRRP是通过一种竞选协议机制来将路由任务交给某台VRRp路由器的。
VRRP用IP组播的方式实现高可用之间通信。
工作时主节点发包，备节点接包，当备节点接收不到主节点发的数据包的时候，就启动接管程序接管主节点的开源。备节点可有多个，通过优先级竞选，但一般keepalived系统运维工作中都是一对。
VRRP使用了加密协议加密数据，但keepalived官方目前还是推荐用明文的方式配置认证类型和密码。
keepalived服务的工作原理：
keepalived高可用是通过VRRP进行通信的，VRRP是通过竞选机制来确定主备的，主的优先级高于备，因此，工作时主会优先获得所有的资源，备节点处于等待状态，当主宕了的时候，备节点就会接管主节点的资源，然后顶替主节点对外提供服务。
在keepalived服务之间，只有作为主的服务器会一直发送VRRP组播包，告诉备它还活着，此时备不会抢占主，当主不可用时，即备监听不到主发送的组播包时，就会启动相关服务接管资源，保证业务的连续性，接管速度最快可以小于1秒。

keepalived默认配置文件

keepalived的主配置文件是/etc/keepalived/keepalived.conf

[root@master ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {       //全局配置
   notification_email {     //定义报警收件人邮件地址
     acassen@firewall.loc
     failover@firewall.loc
     sysadmin@firewall.loc
   }
   notification_email_from Alexandre.Cassen@firewall.loc    //定义报警发件人邮箱
   smtp_server 192.168.200.1    //邮箱服务器地址
   smtp_connect_timeout 30      //定义邮箱超时时间
   router_id LVS_DEVEL          //定义路由标识信息，同局域网内唯一
   vrrp_skip_check_adv_addr
   vrrp_strict
   vrrp_garp_interval 0
   vrrp_gna_interval 0
}

vrrp_instance VI_1 {        //定义实例
    state MASTER            //指定keepalived节点的初始状态，可选值为MASTER|BACKUP
    interface eth0          //VRRP实例绑定的网卡接口，用户发送VRRP包
    virtual_router_id 51    //虚拟路由的ID，同一集群要一致
    priority 100            //定义优先级，按优先级来决定主备角色，优先级越大越优先
    nopreempt               //设置不抢占
    advert_int 1            //主备通讯时间间隔
    authentication {        //配置认证
        auth_type PASS      //认证方式，此处为密码
        auth_pass 1111      //同一集群中的keepalived配置里的此处必须一致，推荐使用8位随机数
    }
    virtual_ipaddress {     //配置要使用的VIP地址
        192.168.200.16
    }
}

virtual_server 192.168.200.16 1358 {    //配置虚拟服务器
    delay_loop 6        //健康检查的时间间隔
    lb_algo rr          //lvs调度算法
    lb_kind NAT         //lvs模式
    persistence_timeout 50      //持久化超时时间，单位是秒
    protocol TCP        //4层协议

    sorry_server 192.168.200.200 1358   //定义备用服务器，当所有RS都故障时用sorry_server来响应客户端

    real_server 192.168.200.2 1358 {    //定义真实处理请求的服务器
        weight 1    //给服务器指定权重，默认为1
        HTTP_GET {
            url {
              path /testurl/test.jsp    //指定要检查的URL路径
              digest 640205b7b0fc66c1ea91c463fac6334d   //摘要信息
            }
            url {
              path /testurl2/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            url {
              path /testurl3/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334d
            }
            connect_timeout 3       //连接超时时间
            nb_get_retry 3          //get尝试次数
            delay_before_retry 3    //在尝试之前延迟多长时间
        }
    }

    real_server 192.168.200.3 1358 {
        weight 1
        HTTP_GET {
            url {
              path /testurl/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334c
            }
            url {
              path /testurl2/test.jsp
              digest 640205b7b0fc66c1ea91c463fac6334c
            }
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}

keepalived实现apache在LVS均衡负载上的高可用实例

ip类型	ip地址
VIP	192.168.74.100
DIP1	192.168.74.3
DIP2	192.168.74.4
RIP1	192.168.74.5
RIP2	192.168.74.6

配置LVS

关闭防火墙和selinux

[root@R1 ~]# systemctl disable --now firewalld
[root@R1 ~]# setenforce 0
[root@R1 ~]# vim /etc/selinux/config 
SELINUX=disabled
SELINUXTYPE=targeted
[root@R2 ~]# systemctl disable --now firewalld
[root@R2 ~]# setenforce 0
[root@R2 ~]# vim /etc/selinux/config 
SELINUX=disabled
SELINUXTYPE=targeted
[root@master ~]# systemctl disable --now firewalld
[root@master ~]# setenforce 0
[root@master ~]# vim /etc/selinux/config 
SELINUX=disabled
SELINUXTYPE=targeted
[root@slave ~]# systemctl disable --now firewalld
[root@slave ~]# setenforce 0
[root@slave ~]# vim /etc/selinux/config 
SELINUX=disabled
SELINUXTYPE=targeted

在调度器上配置VIP和DIP

//配置之前先下载所需要用到的包或者使用本地源
[root@master ~]# dnf -y install ipvsadm
[root@master ~]# dnf -y install keepalived
[root@slave ~]# dnf -y install ipvsadm
[root@slave ~]# dnf -y install keepalived
[root@master ~]# cat /etc/sysconfig/network-scripts/ifcfg-ens33 
TYPE=Ethernet
BOOTPROTO=static
NAME=ens33
DEVICE=ens33
ONBOOT=yes
IPADDR=192.168.74.4
PREFIX=24
GATEWAY=192.168.74.2
DNS1=114.114.114.114
[root@slave ~]# cat /etc/sysconfig/network-scripts/ifcfg-ens33 
TYPE=Ethernet
BOOTPROTO=static
NAME=ens33
DEVICE=ens33
ONBOOT=yes
IPADDR=192.168.74.3
PREFIX=24
GATEWAY=192.168.74.2
DNS1=114.114.114.114

在RS上先关闭arp包的通告和响应然后配置RIP和VIP

[root@R1 ~]# dnf -y install net-tools
[root@R2 ~]# dnf -y install net-tools
[root@R1 ~]# vim /etc/sysctl.conf 
net.ipv4.conf.all.arp_ignore=1
net.ipv4.conf.all.arp_announce=2
[root@R1 ~]# sysctl -p
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2
[root@R1 ~]# ifconfig lo:0 192.168.74.100/32 broadcast 192.168.74.100 up
[root@R1 ~]# route add -host 192.168.74.100 dev lo:0
[root@R1 ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.74.2    0.0.0.0         UG    100    0        0 ens33
192.168.74.0    0.0.0.0         255.255.255.0   U     100    0        0 ens33
192.168.74.100  0.0.0.0         255.255.255.255 UH    0      0        0 lo
[root@R1 ~]# 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 192.168.74.100/0 brd 192.168.74.100 scope global lo:0
       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:b5:5a:ee brd ff:ff:ff:ff:ff:ff
    inet 192.168.74.6/24 brd 192.168.74.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:feb5:5aee/64 scope link 
       valid_lft forever preferred_lft forever

[root@R2 ~]# vim /etc/sysctl.conf 
net.ipv4.conf.all.arp_ignore=1
net.ipv4.conf.all.arp_announce=2
[root@R2 ~]# sysctl -p
net.ipv4.conf.all.arp_ignore = 1
net.ipv4.conf.all.arp_announce = 2
[root@R2 ~]# ifconfig lo:0 192.168.74.100/32 broadcast 192.168.74.100 up
[root@R2 ~]# route add -host 192.168.74.100 dev lo:0
[root@R2 ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.74.2    0.0.0.0         UG    100    0        0 ens33
192.168.74.0    0.0.0.0         255.255.255.0   U     100    0        0 ens33
192.168.74.100  0.0.0.0         255.255.255.255 UH    0      0        0 lo
[root@R2 ~]# 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 192.168.74.100/0 brd 192.168.74.100 scope global lo:0
       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:29:32:7e:b4 brd ff:ff:ff:ff:ff:ff
    inet 192.168.74.5/24 brd 192.168.74.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe32:7eb4/64 scope link 
       valid_lft forever preferred_lft forever

在调度器上添加规则

[root@master ~]# ipvsadm -A -t 192.168.74.100:80 -s rr
[root@master ~]# ipvsadm -a -t 192.168.74.100:80 -r 192.168.74.5:80 -g
[root@master ~]# ipvsadm -a -t 192.168.74.100:80 -r 192.168.74.6:80 -g
[root@master ~]# ipvsadm -Sn > /etc/sysconfig/ipvsadm
[root@master ~]# echo "ipvsadm -Sn > /etc/sysconfig/ipvsadm" >>/etc/rc.d/rc.local
[root@slave ~]# ipvsadm -A -t 192.168.74.100:80 -s rr
[root@slave ~]# ipvsadm -a -t 192.168.74.100:80 -r 192.168.74.5:80 -g
[root@slave ~]# ipvsadm -a -t 192.168.74.100:80 -r 192.168.74.6:80 -g
[root@slave ~]# ipvsadm -Sn > /etc/sysconfig/ipvsadm
[root@slave ~]# echo "ipvsadm -Sn > /etc/sysconfig/ipvsadm" >>/etc/rc.d/rc.local
[root@slave ~]# ipvsadm -C

配置keepalived主配置文件

配置主keepalived

[root@master ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id lb01
}

vrrp_instance VI_1 {
    state MASTER
    interface ens33
    virtual_router_id 100
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass hahahaha
    }
    virtual_ipaddress {
       192.168.74.100 
    }
}

virtual_server 192.168.74.100 80 {
    delay_loop 6
    lb_algo rr
    lb_kind DR
    persistence_timeout 50
    protocol TCP

    real_server 192.168.74.5 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }

    real_server 192.168.74.6 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}
[root@master ~]# systemctl start keepalived
[root@master ~]# systemctl enable keepalived

配置备keepalived

[root@slave ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id lb02
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 100
    priority 90
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass hahahaha
    }
    virtual_ipaddress {
       192.168.74.100
    }
}

virtual_server 192.168.74.100 80 {
    delay_loop 6
    lb_algo rr
    lb_kind DR
    persistence_timeout 50
    protocol TCP

    real_server 192.168.74.5 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }

    real_server 192.168.74.6 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}
[root@slave ~]# systemctl start keepalived
[root@slave ~]# systemctl enable keepalived

查看VIP

在MASTER上查看

[root@master ~]# 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
    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:29:00:40:e3 brd ff:ff:ff:ff:ff:ff
    inet 192.168.74.3/24 brd 192.168.74.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet 192.168.74.100/32 scope global ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe00:40e3/64 scope link 
       valid_lft forever preferred_lft forever

在SLAVE上查看

[root@slave ~]# 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
    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:29:9e:17:ec brd ff:ff:ff:ff:ff:ff
    inet 192.168.74.4/24 brd 192.168.74.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe9e:17ec/64 scope link 
       valid_lft forever preferred_lft forever

让keepalived监控LB

在master上编写脚本

[root@master ~]# mkdir /scripts
[root@master ~]# cat /scripts/notify.sh 
#!/bin/bash
case "$1" in
  master)
            ipvsadm -R < /etc/sysconfig/ipvsadm
  ;;
  backup)
            ipvsadm -C
  ;;
  *)
        echo "Usage:$0 master|backup"
  ;;
esac
[root@master ~]# chmod +x /scripts/notify.sh

在SLAVE上编写脚本

[root@slave ~]# mkdir /scripts
[root@slave ~]# cat /scripts/notify.sh 
#!/bin/bash
case "$1" in
  master)
            ipvsadm -R < /etc/sysconfig/ipvsadm
  ;;
  backup)
            ipvsadm -C
  ;;
  *)
        echo "Usage:$0 master|backup"
  ;;
esac
[root@slave ~]# chmod +x /scripts/notify.sh

配置keepalived加入故障转移脚本

配置主keepalived

[root@master ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id lb01
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 100
    nopreempt
    priority 100
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass hahahaha
    }
    virtual_ipaddress {
       192.168.74.100 
    }
    notify_master "/scripts/notify.sh master"
    notify_backup "/scripts/notify.sh backup"
}

virtual_server 192.168.74.100 80 {
    delay_loop 6
    lb_algo rr
    lb_kind DR
    persistence_timeout 50
    protocol TCP

    real_server 192.168.74.5 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }

    real_server 192.168.74.6 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}
[root@master ~]# systemctl restart keepalived
[root@master ~]# systemctl enable keepalived

配置备keepalived

[root@slave ~]# cat /etc/keepalived/keepalived.conf
! Configuration File for keepalived

global_defs {
   router_id lb02
}

vrrp_instance VI_1 {
    state BACKUP
    interface ens33
    virtual_router_id 100
    priority 90
    nopreempt
    advert_int 1
    authentication {
        auth_type PASS
        auth_pass hahahaha
    }
    virtual_ipaddress {
       192.168.74.100
    }
    notify_master "/scripts/notify.sh master"
    notify_backup "/scripts/notify.sh backup"
}

virtual_server 192.168.74.100 80 {
    delay_loop 6
    lb_algo rr
    lb_kind DR
    persistence_timeout 50
    protocol TCP

    real_server 192.168.74.5 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }

    real_server 192.168.74.6 80 {
        weight 1
        TCP_CHECK {
            connect_port 80
            connect_timeout 3
            nb_get_retry 3
            delay_before_retry 3
        }
    }
}
[root@slave ~]# systemctl restart keepalived
[root@slave ~]# systemctl enable keepalived

测试验证

因为开启了不抢占，即使master主机宕机恢复了也不会恢复成为主

[root@master ~]# 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
    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:29:00:40:e3 brd ff:ff:ff:ff:ff:ff
    inet 192.168.74.4/24 brd 192.168.74.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet 192.168.74.100/32 scope global ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe00:40e3/64 scope link 
       valid_lft forever preferred_lft forever
[root@master ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.168.74.100:80 rr
  -> 192.168.74.5:80              Route   1      0          0         
  -> 192.168.74.6:80              Route   1      0          0     
[root@slave ~]# 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
    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:29:9e:17:ec brd ff:ff:ff:ff:ff:ff
    inet 192.168.74.3/24 brd 192.168.74.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe9e:17ec/64 scope link 
       valid_lft forever preferred_lft forever
[root@slave ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
[root@master ~]# poweroff 
[root@master ~]# 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
    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:29:9e:17:ec brd ff:ff:ff:ff:ff:ff
    inet 192.168.74.4/24 brd 192.168.74.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe9e:17ec/64 scope link 
       valid_lft forever preferred_lft forever
[root@master ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
[root@slave ~]# 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
    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:29:00:40:e3 brd ff:ff:ff:ff:ff:ff
    inet 192.168.74.3/24 brd 192.168.74.255 scope global noprefixroute ens33
       valid_lft forever preferred_lft forever
    inet 192.168.74.100/32 scope global ens33
       valid_lft forever preferred_lft forever
    inet6 fe80::20c:29ff:fe00:40e3/64 scope link 
       valid_lft forever preferred_lft forever
[root@slave ~]# ipvsadm -Ln
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
  -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
TCP  192.168.74.100:80 rr
  -> 192.168.74.5:80              Route   1      0          0         
  -> 192.168.74.6:80              Route   1      0          0

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