CentOS 7 DNS installation and configuration

Actual combat environment (CentOS7) 

VIP 10.211.55.180 (virtual IP) 
LVS1 10.211.55.151 (main LVS) 
LVS2 10.211.55.152 (standby LVS) 
RS1 10.211.55.171 (real server 1) 
RS2 10.211.55.172 (real server 2) 


initialization environment all Node 
iptalbes -F #Clear the firewall 
systemctl stop firewalld #Turn off the firewall 
systemctl disable firewalld #Stop the firewall from booting up 
setenforce 0 #Temporarily turn off selinux 
sed -i's/^SELINUX=.*$/SELINUX=disabled/g' /etc/ selinux/config 
#Close selinux 
date #Time 
yum -y install epel-release 

#Install epel source LVS1, 2 operation 

1, install keepalived ipvsadm 

yum -y install keepalived ipvsadm 


[root@localhost ~]# lsmod |grep ip_vs #check ipvs module  
ip_vs_rr 12600 1
ip_vs 145497 3 ip_vs_rr
nf_conntrack          139264  9 ip_vs,nf_nat,nf_nat_ipv4,nf_nat_ipv6,xt_conntrack,nf_nat_masquerade_ipv4,nf_conntrack_netlink,nf_conntrack_ipv4,nf_conntrack_ipv6
libcrc32c              12644  4 xfs,ip_vs,nf_nat,nf_conntrack 



2、配置keepalived  （LVS1、2）

2.1 修改keepalived的配置文件
[root@localhost ~]# cd /etc/keepalived/
[root@localhost keepalived]# cat 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 LVS_DEVEL
   vrrp_skip_check_adv_addr 
#   vrrp_strict    #
   vrrp_garp_interval 0
   vrrp_gna_interval 0 
} 

vrrp_instance VI_1 { 
    state MASTER #LVS1 here is the MASTER, then LVS2 is changed to BACKUP 
    interface eth0 #CENTOS7 ens33 
    virtual_router_id 51 #If the master and backup are consistent 
    priority 100 #LVS1 is 100, then LVS2 is 100 , Such as 90, the greater the weight, which side VIP will float on 99 89 
    advert_int 1 
    authentication { 
        auth_type PASS 
        auth_pass 1111 
    } 
    virtual_ipaddress { 
        10.211.55.180 #VIP 
    } 
} 

virtual_server 10.211.55.180 80 {#VIP 
    delay_loop 6 
    lb_algo rr
    lb_kind DR  
    persistence_timeout 50
    protocol TCP 

    real_server 10.211.55.171 80 {#Back-end RS1 detection 
        weight 1 
        TCP_CHECK { 
            connect_timeout 3 
            nb_get_retry 3 
            delay_before_retry 3 
            connect_port 80 
        } 
    } 
    real_server 10.211.55.172 80 {#Back-end RS2 detection 
        weight 1 
        TCP_CHECK { 
            connect_timeout 3 
            nb_get_retry delay 3 
            nb_get_retry 
            connect_port 80 
        } 
    } 
} 


2.2 Set boot up (LVS1, 2) 
systemctl enable keepalived 
systemctl start keepalived 


3. Configure LVS, execute the following script (LVS1, 2), and set the script to boot up

vi /opt/lvs_dr.sh 
#!/bin/sh 
# description: Start LVS of Director server 
VIP=10.211.55.180 
RIP1=10.211.55.171 
RIP2=10.211.55.172 
case "$1" in 
    start) 
        echo "start LVS of Director Server " 
# set the Virtual IP Address and sysctl parameter 
# /sbin/ifconfig eth0:0 $VIP broadcast $VIP netmask 255.255.255.255 up 
# route add -host $VIP dev eth0:0 
       echo "1" >/proc/sys/net /ipv4/ip_forward 
#Clear IPVS table 
       /sbin/ipvsadm -C 
#set LVS 
/sbin/ipvsadm -A -t $VIP:80 -s rr # -p 600 #If you need session persistence, cancel the -p 600 here Comment 
#Run LVS
/sbin/ipvsadm -a -t $VIP:80 -r $RIP1:80 -g
/sbin/ipvsadm -a -t $VIP:80 -r $RIP2:80 -g 
      /sbin/ipvsadm 
       ;; 
    stop) 
        echo "close LVS Directorserver" 
        echo "0" >/proc/sys/net/ipv4/ip_forward 
        / sbin/ipvsadm -C 
      # /sbin/ifconfig eth0:0 down 
        ;; 
    *) 
        echo "Usage: $0 {start|stop}" 
        exit 1 
esac 

chmod +x /opt/lvs_dr.sh #Add execution permission 

echo "/opt/ lvs_dr.sh start" >>/etc/profile #Boot self-start 


4. Configure RS operation, perform the following operations (RS1, 2) to 

install nginx 
yum -y install nginx #RS1, 2 install 

echo 10.211.55.171 >/usr/ share/nginx/html/index.html #RS1 operation 
echo 10.211.55.172 >/usr/share/nginx/html/index.html #RS2Upper operation


Set up the RS script and set it to start automatically  
vi /opt/lvs_rs.sh

#!/bin/bash 
VIP=10.211.55.180 
/sbin/ifconfig lo:0 $VIP broadcast $VIP netmask 255.255.255.255 up 
/sbin/route add -host $VIP dev lo:0 
echo “1″ >/proc/sys/net/ipv4/conf/lo/arp_ignore 
echo “2″ >/proc/sys/net/ipv4/conf/lo/arp_announce 
echo “1″ >/proc/sys/net/ ipv4/conf/all/arp_ignore 
echo “2″ >/proc/sys/net/ipv4/conf/all/arp_announce 
sysctl -p 
#end 
This operation is to bind a virtual IP address on the loopback device and set it The subnet mask is 255.255.255.255, which maintains intercommunication with the virtual IP on the Director Server, and then prohibits the local ARP request. 
Since the virtual ip, which is the VIP address above, is shared by Director Server and all Real servers, if there is an ARP request for the VIP address, if the Director Server responds to all Real servers, there will be a problem. Therefore, it needs to be prohibited. Real server responds to the ARP request. The role of the lvsrs script is to make Real Server not respond to arp requests. 

chmod + /opt/lvs_rs.sh #Add execution permissions
echo "/opt/lvs_rs.sh "#Startup automatically after booting 



5. Test 
Find a client and execute the following command 
->$ for i in `seq 20`;do curl 10.211.55.180;done 
10.211.55.171 
10.211.55.172 
10.211 .55.171 
10.211.55.172 
10.211.55.171 
10.211.55.172 
10.211.55.171 
10.211.55.172 
10.211.55.171 
10.211.55.172 
10.211.55.171 
10.211.55.172 
10.211.55.171 
10.211.55.172 
10.211.55.171 
10.211.55.172 
10.211.55.171 
10.211.55.172 
10.211.55.171 
10.211.55.172