Caching name servers, also called DNS caches, store DNS query results for a period of time determined in the configuration (time-to-live) of each domain-name record. DNS caches improve the efficiency of the DNS by reducing DNS traffic across the Internet, and by reducing load on authoritative name-servers, particularly root name-servers. Because they can answer questions more quickly, they also increase the performance of end-user applications that use the DNS. Read more
This article will help you to setup caching nameserver on your CentOS/RHEL 6 system.
Step 1: Install BIND Packages
Install bind packages using below command. In CentOS/RHEL 6 chaching-nameserver package has been included with bind package.
# yum install bind bind-chroot
Step 2: Create Configuration File
Copy bind configuration file from bind sample files using below command. Change the path of files as per version you have installed.
# cd /var/named/chroot/etc
# cp /usr/share/doc/bind-9.8.2/sample/etc/named.conf .
# cp /usr/share/doc/bind-9.8.2/sample/etc/named.rfc1912.zones .
Step 3: Update Configuration File
Edit bind configuration file in your favorite editor and make necessary changes as per below settings or use below configuration.
#vi /var/named/chroot/etc/named.conf
options {
listen-on port 53 { 127.0.0.1; any; };
listen-on-v6 port 53 { ::1; };
directory "/var/named";
dump-file "/var/named/data/cache_dump.db";
statistics-file "/var/named/data/named_stats.txt";
memstatistics-file "/var/named/data/named_mem_stats.txt";
allow-query { localhost; any; };
allow-query-cache { localhost; any; };
recursion yes;
dnssec-enable yes;
dnssec-validation yes;
dnssec-lookaside auto;
/* Path to ISC DLV key */
bindkeys-file "/etc/named.iscdlv.key";
managed-keys-directory "/var/named/dynamic";
};
logging {
channel default_debug {
file "data/named.run";
severity dynamic;
};
};
include "/etc/named.rfc1912.zones";
Now update required permissions on configuration files using below command.
# chown root:named named.conf named.rfc1912.zones
Step 4: Check Configuration File
We recommend to check DNS configuration file before restarting service.
# named-checkconf named.conf
Step 5: Restart Bind Service
Now installation of bind service has been completed. Lets start bind (named) service using following command.
# service named restart
Enable auto start bind service on system boot.
# chkconfig named on
Step 6: Finally Test Caching Only DNS
Send query to your dns server directly using below command.
Syntax: nslookup <domainname> <caching dns server name/ip>
# nslookup yahoo.com 192.168.1.1
[Sample Output:]
Address: 192.168.1.1#53 nslookup yahoo.com Server: 192.168.1.1
Address: 192.168.1.1#53
Non-authoritative answer: Name: yahoo.com Address: 74.6.143.25 Name: yahoo.com Address: 74.6.143.26 Name: yahoo.com Address: 74.6.231.20 Name: yahoo.com Address: 74.6.231.21 Name: yahoo.com Address: 98.137.11.163 Name: yahoo.com Address: 98.137.11.164 Name: yahoo.com Address: 2001:4998:24:120d::1:1 Name: yahoo.com Address: 2001:4998:44:3507::8000 Name: yahoo.com Address: 2001:4998:44:3507::8001 Name: yahoo.com Address: 2001:4998:124:1507::f000 Name: yahoo.com Address: 2001:4998:124:1507::f001 Name: yahoo.com Address: 2001:4998:24:120d::1:0
troubleshooting :- #tail /var/log/messages -fAll of the addresses are IPv6. Seems an IPv6 issue, you probably have no IPv6 networking configured. Disable IPv6 suport in Bind:
Edit /etc/sysconfig/named and set:
OPTIONS="-4"
Then restart bind:
service named restart
