Understanding DNS & Troubleshooting Common DNS Errors

DNS (Domain name system) may not be known to most people who use internet but it is the real backbone and the invisible force driving the whole internet without which we would be seeing numbers and IPs. The whole meaning of domain names exist today just because of DNS.

INTRODUCTION

The simplest way of explaining DNS in one line is to map domain name to IP address. I am not sure how many would know …

I have been quite intrigued with the working of these URL shortner scripts and surprisingly most of them employ an ingenious solution to compress the URL to a shortened one.

http://example.com/fe45 ——-> http://corpocrat.com/blah/page.htm

The answer is base36 encoding. why base36? because it can contain 26 alphabets and 10 numbers in the output. This is surprisingly simple way of encoding a URL.

Base 36 is nothing but, you keep on dividing a number by 36, collect its reminders (or modulo) and map them …

How to check IPs on same subnet?

In many cases, you might want to check whether an ip address falls under a same subnet or not. It can be done both in perl and php using the Network library.

For PHP use Net IP4 library
For PERL use Net::IP library

<?php
// check for IP falls in same subnet or not
include("Net/IPv4.php");

$objIP = new Net_IPv4();

echo $objIP->ipInNetwork("192.xx.xx.xx", "192.xx.xx.x/24") ? "Same Subnet" : "Outside the Subnet";
?>

In perl you can use Net::IP module

#!/usr/bin/perl

use NetAddr::IP;

my $netwrk = NetAddr::IP->new(‘192.xx.xx.x/24′);
my $ip …

DNS-Test :: Free dns checking tool script!

I a wrote a dns checking script perl in script (CGI available) which can perform various tests for dns including…

* Checking for Nameservers NS records
* Website IP address (A Record)
* NS records from parent servers (root server)
* Check for LAME nameservers (Authoritative nameservers)
* Check for Open DNS server
* Check for Zone Transfer (AXFR)
* Check for NS ips on same subnet
* Check for SOA record (with TTL, Referesh etc…)
* Check for Stealth Nameservers
* CNAME …

Perl Net DNS Tutorial for Querying DNS Servers

Perl is really a very powerful language when it comes to low level system programming requiring intensive processing. Perl Net::DNS library can be used to write powerful web applications involving DNS lookups and queries. Before you start this perl programming you want want to understand certain dns concepts and experiment with dig tool. I would recommend reading this Dig tutorial

In this tutorial i will show you how easy it is to write …

Using Dig tool for DNS lookups and Nameserver query

Dig tool in linux has become so important tool for querying dns servers and
fixing many dns related issues. I will show the easy way to use dig tool for
complex dns queries.

Lookup DNS Nameservers

Let us see what nameservers (NS records) are availale for the domain google.com.
The additional section automatically maps the corresponding NS records to their
IP address.

dig google.com NS

; <<>> DiG 9.2.4 <<>> google.com …

Install PEAR for php in Linux

It is very easy to install PEAR package for php. It lets you to install many many php extensions easily without compiling the source packages.

If you get

pear – command not found

then it means pear is not installed in your server. To install it just follow the steps below at the command prompt.

Download the installation php file from http://pear.php.net/go-pear.

wget http://pear.php.net/go-pear

Rename to php file

cp go-pear go-pear.php

Run the php script from commandline.

php go-pear.php

and you will see …

First thing to check when buying a digital camera!

Well! it may sound weird! Having owned many digital cams including of kodak and nikon i learnt a valuable lesson.

The Batteries! I am soon off to buying a good digital camera and the first thing i would check is for a battery that comes with lithium ion (like battery used in mobiles) and NOT the AA battery NiMH/Alkaline cells. I really hate those cells type and everytime those cells exhaust and …

The Bourne Conspiracy is a good action game for PS3 console

I really liked the game especially those melee hand fights are superb and this game is a very good mix of hand fights and shooting. I just completed the game yesterday and it can be completed with 12-15 hours of gameplay. The game graphics is amazing and the storyline is almost the same as the bourne identity movie. The car driving is so much fun and its a very …

Best fighting games for PS3

If you love fighting games in PS3 platform then i would recommend to buy the following games which are absolutely superb.

Street Fighter IV (superb)
Mortal Kombat vs DC Universe (Good)
Soulcalibur IV (Good)
Virtua Fighter 5 (Good)

and of course!

Fight Night Round 4 (my favorite)

Before buying a game do check for various reviews and screenshots as each of the games are different and playing styles suited to your liking. As per the pricing Virtua fighter 5 should …