updated: 12/21/2022
Round-Robin DNS Setup is a great way to ensure your website or online application runs smoothly and efficiently. It provides an effective load-balancing technique that improves the performance of your website by distributing incoming requests across multiple sources.
This setup helps to reduce downtime, as well as eliminate single points of failure. Through the strategic use of multiple IP addresses and Domain Name System (DNS) records, Round-Robin DNS setups help provide a reliable and stable experience for your users.
Round-Robin DNS Setup
Round-robin DNS provides load distribution across multiple machines using the same hostname but each having its own IP. Each request to the DNS server is routed to a different machine in sequential order.
Configuration of round-robin DNS uses the Berkeley Internet Name Domain(BIND) named daemon. BIND uses zone files to define hostnames with address records.
An example of a round-robin BIND zone file:
nfs.test.local IN A 10.10.0.101
nfs.test.local IN A 10.10.0.102
nfs.test.local IN A 10.10.0.103
Install and Setup
This applies to RHEL.
Make sure the BIND package is installed. Do not install the bind-chroot package:
Make sure the BIND package is installed. Do not install the bind-chroot package:
yum install bind
The install creates the named service and the following configuration files:
/etc/named.conf #read when named service starts
/var/named #working directory for the named service
/var/named/dynamic #directory for the zone data
Edit named.conf to look like the following:
//
// /etc/named.conf
//
options {
listen-on port 53 { any; };
directory “/var/named/”; # states working directory
allow-query { any; }; # lists which hosts can query the nameserver
recursion yes;
forwarders { x.x.x.x; x.x.x.x; }; # site dns servers
};
logging {
channel default_debug {
file “data/named.run”;
severity dynamic;
};
};
//
// Zone Definitions
//
zone “localhost” IN {
type master;
file “named.localhost”;
};
zone “test.local” IN {
allow-transfer { any; };
file “dynamic/nfstest.main”; # zone configuration file
type master; # indicates it’s the owner of zone file
};
Edit the zone file to look like the following, adding you own hostname to IP mappings:
//
// /var/named/dynamic/nfstest.main
//
//
$TTL 1d # how long a zone record is valid
$ORIGIN test.local. # allows you to append the domain name to unqualified records
@ IN SOA s01.test. root ( #Start of Authority record
20120527 ;serial
4H ;refresh
1H ;retry
1W ;expiry
1D ) ;minimum
;
IN NS s01.test.local. # states the nameserver
; IN NS secondary.test.local.
;
;********************************
;* Domain Address Information *
;********************************
;
; Local Host
;
localhost IN A 127.0.0.1
;
; Machine Names
;
; Private Network (10.10.0.0/24)
;
;
n01 IN A 10.10.0.01
n02 IN A 10.10.0.02
n03 IN A 10.10.0.03
n04 IN A 10.10.0.04
n05 IN A 10.10.0.05
n06 IN A 10.10.0.06
n07 IN A 10.10.0.07
n08 IN A 10.10.0.08
n09 IN A 10.10.0.09
n10 IN A 10.10.0.10
;
fs01 IN A 10.10.0.21
fs02 IN A 10.10.0.22
s01 IN A 10.10.0.23
;
; Clustered NFS # this is the round robin entry
nfs IN A 10.10.0.101
nfs IN A 10.10.0.102
nfs IN A 10.10.0.103
nfs IN A 10.10.0.101
nfs IN A 10.10.0.102
nfs IN A 10.10.0.103
Start the named service:
service named start
chkconfig named on
Configure the clients to point to the DNS nameserver:
root@client# vi /etc/resolv.conf
search nfs.test.local
nameserver 10.10.0.23 # add your nameserver IP
nameserver x.x.x.x # add site nameserver
Now whenever a client machine queries the name ‘nfs’ the response from the DNS server will rotate through the entries above.
