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Caching Nameserver And BIND-9 Together

January 24th, 2007 at 1:58 pm (Linux Articles, Server Administration)

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Author: Nayyar Ahmad

Contact: nayyares *AT* gmail *DOT* com

Dedication: To my pets - boby and tavi.

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Preface:

Some times, we are required to resolve our Internal domains at local nameserver while External (Internet) domains from ISP’s nameserver. There are different solutions to this problem, but in this howto, we are going to solve it through configuring combination of caching-nameserver and BIND 9 together.

Theory Behind Caching-Namerserver and BIND 9:

Caching-Nameserver is a type of nameserver that will resolve a web address (domain name) from its next or master DNS, and will keep those entries in cache, after first time resolution it will resolve DNS queries locally, untill its TTL (Time To Live) is expired.

BIND 9 is used to resolve domain resolution queries from it own database, as it is SOA (Start Of Authority).

So now it is clear that in our setup the caching-nameserver will be used to resolve domain names exist on Internet or External, while BIND 9 will be used to resolve domain names exits in our network or Internal.

Now we have caching-nameserver and BIND 9 hammer in our hands, lets start fixing it.

1. Installing caching nameserver/ BIND 9:

Simplest method to install all required packages for this howto is,

$yum install caching-nameserver bind*

same for apt based system, but if you d’nt have yum or apt configured you can install following packages from your distribution cds, I am not mentioning packages versions as it depends on your distribution i.e.

Required Packages: bind , bind-chroot, bind-utils, bind-lib, caching-nameserver

after installation of these packages we have to find either we have all required packges installed or not, to do so, use following command.

$rpm -qa bind*

$rpm -qa caching-nameserver

The above commands work fine, only if you are working on RPM based Linux Distro, otherwise check according to your own distro method. Now if you are able to see all mentioned packges , this means you are about to hit your nameserver with BIND hammer

2. Editing named.conf :

First of all we have to register our domain name with BIND, for the reason, we will edit named.conf, open it and type following lines.

$vi /etc/named.conf

now type following lines i.e.

zone “cbtcandy.org” IN {
        type master;
        file ” cbtcandy.org.zone”;
        allow-update { none; };
};

you should change cbtcandy.org with your own domain name.

3. Starting Bind Daemon:

you can start bind daemon/service to check whether your named.conf is written perfact, now you can do this by different method, it will state two of them

For Redhat, Centos, Fedora type system, give following command,

$ service named start

For Suse, Debian type systems,

$/etc/rc.d/rc.bind start

Now if Bind daemon is started successfully that means we are half way done.

4. Setting Bind Daemon Starts On Boot:

The following command will work perfact in Redhat, Centos, Fedora, but I
am not sure about other distros, so better you find its equivalent.

$chkconfig named on –level 35

5. Zone File Creation:

Now there is an issue where is my shotgun ?

i.e.

if you have installed bind-chroot, then you will be creating your domain zone file in /var/named/chroot/var/named/ directory, and then will make a softlink to /var/named/ directory, but if you d’nt have installed this chroot packge, then you are going to create zone file directly in /var/named/ directory.

Now following command works fine, when you have bind-chroot:

$ vi /var/named/chroot/var/named/cbtcandy.org.zone

OR (when bind-chroot is not installed)

$ vi /etc/named/cbtcandy.org.zone

and type the following lines into your zone file:

$TTL    86400
@               IN SOA @ nayyares.gmail.com. (
                                        42              ; serial (d. adams)
                                        3H              ; refresh
                                        15M             ; retry
                                        1W              ; expiry
                                        1D )            ; minimum
@               IN NS           nameserver.cbtcandy.org.
nameserver      IN A            192.168.1.1
cache           IN A            192.168.1.2
www             IN A            192.168.1.3
portal          IN A            192.168.1.4

you can add as much records as you wish in this file.

Note: Here I am assuming that our DNS machine name is nameserver and LAN subnet is on 192.168.1.0/24 , you can change this according to your situation.

now following step is only when you have created zone file in /var/names/chroot/var/named/ directory.

$ ln -s /var/named/chroot/var/named/cbtcandy.org.zone /var/named/cbtcandy.org.zone

6. Editing resolv.conf :

Now to tell our nameserver machine about the order it will look for name resolution, we have to edit /etc/resolv.conf file,

$vi /etc/resolv.conf

and write following two lines, but keep them in same order, as we want to first resolve domain resolution query by caching-name server, so we will keep 127.0.0.1 line first, in this file.

nameserver 127.0.0.1

nameserver 212.96.24.1

Note: It is assume that your ISP’s nameserver machine IP is 212.96.24.1 .

7. Setting Up Host Name:

To setup your hostname according to your domain, we will edit /etc/sysconfig/network file i.e.

$ vi /etc/sysconfig/network

Here type following line:

HOSTNAME= nameserver.cbtcady.org

8. Restarting BIND Daemon:

$ service named restart (Redhat,Fedora,Centos)

$ /etc/rc.d/rc.bind restart (Suse,Debian)

9. Testing: