How to install and configure Caching-only DNS server in Debian

####################################################################

       @@@@ Implementing a caching-only DNS on Debian @@@@@

####################################################################

Step 1: 

                # apt-get install bind9 dnsutils

Step 2:

The config for bind in Debian is a subdirectory structure in /etc/bind.

                # cd /etc/bind

Step 3:

For a simple caching-only server, we have to leave /etc/bind/named.conf untouched . We just modify /etc/bind/named.conf.options  file to give the  forwarders IP address:

                # vim named.conf.options

-----------------------------------------------------------------------------------------------------

options {

        directory "/var/cache/bind";

        // If there is a firewall between you and nameservers you want

        // to talk to, you may need to fix the firewall to allow multiple

        // ports to talk.  See http://www.kb.cert.org/vuls/id/800113

        // If your ISP provided one or more IP addresses for stable

        // nameservers, you probably want to use them as forwarders.

        // Uncomment the following block, and insert the addresses replacing

        // the all-0's placeholder.

        forwarders {

             // OpenDNS servers

             208.67.222.222;  {Your ISP's DNS Address}

             208.67.220.220;  {Your ISP's DNS Address}

             // ADSL router

             192.168.1.1;  {If gateway router is available}

        };

        // Security options

        listen-on port 53 { 127.0.0.1; 192.168.1.100; };

        allow-query { 127.0.0.1; 192.168.1.0/24; };

        allow-recursion { 127.0.0.1; 192.168.1.0/24; };

        allow-transfer { none; };

        auth-nxdomain no;    # conform to RFC1035

        // listen-on-v6 { any; };

};

------------------------------------------------------------------------------------------------------

Step 4:

Restart bind to load the new configuration:

                # /etc/init.d/bind9 restart

                or

                # service bind9 restart

Step 5:

Update /etc/resolv.conf, so DNS queries will be performed locally:

nameserver 127.0.0.1

Step 6: Test our caching only dns server

                # dig www.yahoo.com

main portion of the output.................

;; Query time: 433 msec   [First time dig]

;; SERVER: 127.0.0.1#53(127.0.0.1)

;; WHEN: Mon May 24 05:18:21 2010

;; MSG SIZE  rcvd: 265

//////////////////////////////////////////

;; Query time: 2 msec   [Second time dig]

;; SERVER: 127.0.0.1#53(127.0.0.1)

;; WHEN: Mon May 24 05:18:21 2010

;; MSG SIZE  rcvd: 265

Important: we have to be more careful about the  server ip address that means from which dns the query is responded. (SERVER: 127.0.0.1#53(127.0.0.1))

Check for possible syntax errors:

root@server:~# named-checkconf

How Do I See Current Cache?

Type the following command to dump cache(s) to the dump file called /var/cache/bind/named_dump.db:

# rndc dumpdb

# less /var/cache/bind/named_dump.db

# grep 'yahoo.com' /var/cache/named/named_dump.db

How Do I Debug BIND 9 Caching Server Problems?

The first place is to look error or warnings in /var/log/syslog file using the grep, cat, more, less or awk commands:

# tail -f /var/log/syslog

Is Port 53 Open?

Next make sure BIND 9 caching server is running on default port 53, run:

# netstat -tulpn | grep :53