How to configure a highly available DNS cluster on Linux

How to configure a highly available DNS cluster on Linux

Introduction:
With the rapid development of the Internet, DNS (Domain Name System), as one of the important network infrastructures, plays the role of domain name Key role translated to IP address. In a high-traffic network environment, the high availability of the DNS server becomes critical. This article describes how to configure a highly available DNS cluster on a Linux system and provides some code examples.

1. Install DNS server:
   First, we need to install the DNS server on the Linux system. This article takes the commonly used BIND (Berkeley Internet Name Domain) server as an example for configuration. Execute the following command to install BIND:

sudo apt-get update
sudo apt-get install bind9

2. Configure the primary DNS server:
   Next, we need to configure it on the primary DNS server. Open BIND's main configuration file /etc/bind/named.conf.local and add the following content:

zone "example.com" {
    type master;
    file "/etc/bind/db.example.com";
    allow-transfer { IP_ADDRESS_OF_SECONDARY_DNS_SERVER; };
};

Note that replace example.com for your own domain name, and replace IP_ADDRESS_OF_SECONDARY_DNS_SERVER with the IP address of your secondary DNS server.

Then, create the domain name resolution file /etc/bind/db.example.com and add the following content:

;
; BIND data file for example.com
;
$TTL    604800
@       IN      SOA     ns1.example.com. admin.example.com. (
                  3        ; Serial
             604800         ; Refresh
              86400         ; Retry
            2419200         ; Expire
             604800 )       ; Negative Cache TTL
;
@       IN      NS      ns1.example.com.
@       IN      A       IP_ADDRESS_OF_PRIMARY_DNS_SERVER
ns1     IN      A       IP_ADDRESS_OF_PRIMARY_DNS_SERVER
www     IN      CNAME   example.com.

Make sure to add example.com# Replace ## with your own domain name and IP_ADDRESS_OF_PRIMARY_DNS_SERVER with the IP address of your primary DNS server.

Configure the secondary DNS server:
3. Next, we need to configure the secondary DNS server. Open BIND's main configuration file
   /etc/bind/named.conf.local and add the following:

zone "example.com" {
    type slave;
    file "/etc/bind/db.example.com";
    masters { IP_ADDRESS_OF_PRIMARY_DNS_SERVER; };
};

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example.com Replace # with your own domain name and IP_ADDRESS_OF_PRIMARY_DNS_SERVER with the IP address of the primary DNS server.

Start the DNS server:
4. After completing the configuration, we need to start the DNS server and make it start automatically when the system starts. Execute the following commands to start the primary DNS and secondary DNS respectively:
   

sudo systemctl start bind9
sudo systemctl enable bind9

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Configure high availability:
5. In order to achieve highly available DNS services, we can use load balancing and failover technology. Here we use Keepalived and HAProxy to achieve load balancing and failover.
   

sudo apt-get install keepalived
sudo apt-get install haproxy

/etc/keepalived/keepalived.conf and add the following content:

global_defs {
    router_id LVS_DEVEL
}

vrrp_instance VI_1 {
    state MASTER
    interface eth0
    virtual_router_id 51
    priority 100

    virtual_ipaddress {
        IP_ADDRESS_OF_DNS_CLUSTER
    }
}

IP_ADDRESS_OF_DNS_CLUSTER Replace with the virtual IP address used for load balancing.

/etc/keepalived/keepalived.conf and add the following content:

global_defs {
    router_id LVS_DEVEL
}

vrrp_instance VI_1 {
    state BACKUP
    interface eth0
    virtual_router_id 51
    priority 99

    virtual_ipaddress {
        IP_ADDRESS_OF_DNS_CLUSTER
    }
}

IP_ADDRESS_OF_DNS_CLUSTER Replaced with the virtual IP address used for load balancing.

/etc/haproxy/haproxy.cfg on the primary DNS server and secondary DNS server respectively, refer to the following example:

frontend dns_cluster
    bind IP_ADDRESS_OF_DNS_CLUSTER:53
    mode tcp
    default_backend dns_servers

backend dns_servers
    mode tcp
    balance roundrobin
    server primary_dns IP_ADDRESS_OF_PRIMARY_DNS_SERVER:53 check
    server secondary_dns IP_ADDRESS_OF_SECONDARY_DNS_SERVER:53 check

IP_ADDRESS_OF_DNS_CLUSTER with the virtual IP address used for load balancing, and replace IP_ADDRESS_OF_PRIMARY_DNS_SERVER and IP_ADDRESS_OF_SECONDARY_DNS_SERVER with the IP addresses of the primary and secondary DNS servers.

Startup and Test:
6. After completing the configuration, we start the Keepalived and HAProxy services and check the availability of the DNS service. Execute the following commands on the primary DNS server and secondary DNS server to start the service:
   

sudo systemctl start keepalived
sudo systemctl start haproxy

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dig) to test whether the DNS service is working properly. For example, execute the following command:

dig example.com @IP_ADDRESS_OF_DNS_CLUSTER

IP_ADDRESS_OF_DNS_CLUSTER with the virtual IP address used for load balancing.

Through the introduction and code examples of this article, you have learned how to configure a highly available DNS cluster on a Linux system. Through load balancing and failover technology, you can improve the availability and performance of your DNS server and ensure the stability of network services. I wish you success in configuring a highly available DNS cluster!

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