Domain Name Server (DNS)

How DNS (Domain Name Server) works?

When we type a web address in our browser [like www.google.com] and hit go, the request goes to our local ISP servers who translate that domain name into a hard-to-remember IP address [like 66.102.7.104]

While this address resolution mechanism is transparent to the average internet user, it can sometimes be the main reason for slow internet access if the DNS servers of your ISP are acting choppy or not working at all.

To overcome these problems, you can consider changing your DNS server name to a more reliable but free service called OpenDNS. There's no software to install, just a small tweak in your internet connection settings.

We just replaced the default DSN server address of our ISP with the OpenDNS servers which are :

The DNS server can be changed from the TCP/IP Properties section. [Control Panel -> Network Connections -> Local Network Connection -> TCP IP Properties]

Why OpenDNS is good ? Your domain resolution request to OpenDNS is executed from the nearest physical location and the address are also cached at their end. Therefore you notice faster internet browsing.

Second OpenDNS would auto-correct misspelled domain names [or typos]. For instance, if you type www.gooogle.com by mistake, you'll be redirected to www.google.com without any interventation. The other advantage is that you have a much safer browsing experience since OpenDNS would prevent you from visiting a scam website by error.

Some precautions before using OpenDNS

1. In the extreme situation when OpenDNS servers go down, you should keep the address of your ISP DNS servers handy.

2. You can turn off the phishing protection or auto typo correction by visiting the OpenDNS preferences page.

3. Some users might have privacy concerns with OpenDNS while some dislike seeing ads when they mis-spell domain names. The choice is completely your's here.

NETWORK PING

Network Ping - Testing Commands and Utilities

In computer networking, ping is a process for sending test messages from one computer to another to check the health of network connections. Ping tests are run using various software commands and utility programs.

What is Ping?
Ping is the name of a standard utility used to test network connections. Ping utilities are part of Windows, Mac OS X and Linux as well as some network routers and game consoles.

What Is a Computer Ping Test?
A ping test determines the latency (communication delay) between your computer and another computer on a network. Using ping tests can be useful when troubleshooting network problems, and they are also an important consideration for online gaming and other interactive applications.

IP Configuration

IPCONFIG

Configure IP (internet protocol configuration)

Syntax

IPCONFIG /all Display full configuration information.

IPCONFIG /release [adapter] Release the IP address for the specified adapter.

IPCONFIG /renew [adapter] Renew the IP address for the specified adapter.

IPCONFIG /flushdns Purge the DNS Resolver cache.

IPCONFIG /registerdns Refresh all DHCP leases and re-register DNS

names.

IPCONFIG /displaydns Display the contents of the DNS Resolver Cache.

IPCONFIG /showclassid adapter Display all the DHCP class IDs allowed for adapter.

IPCONFIG /setclassid adapter [classid] Modify the dhcp class id.

If the Adapter name contains spaces, use quotes: "Adapter Name"
wildcard characters * and ? allowed, see the examples below

The default is to display only the IP address, subnet mask and default gateway for each adapter bound to TCP/IP.

For Release and Renew, if no adapter name is specified, then the IP address leases for all adapters bound to TCP/IP will be released or renewed.

For Setclassid, if no ClassId is specified, then the ClassId is removed.

HOW TO NETWORK COMPUTERS

This article is a basic understanding on how to create a simple network in which two computers are connected together for the purpose of sharing data, sharing of devices (printers, scanners..etc.) and connected a network game.

1. Choose a Network Address

• Any network address will do for this purpose, so long as you understand the basics of how IPv4 works as explained below.
• IPv4 (IP ver. 4) addresses are written like this: xxx.xxx.xxx.xxx (four number groups separated by three dots), in all RFC-1166 compliant countries. Each number ranges from 0 to 255. This is known as "Dotted Decimal Notation" or "Dot Notation" for short. The address is divided into two portions: the network portion and the host portion.
  
  For "Classful" networks, the network and host portions are as follows:
  ("n" represents the network portion, "x" represents the host portion)
  
  When the first number is 0 to 127 - nnn.xxx.xxx.xxx (ex. 10.xxx.xxx.xxx)
  These are known as "Class A" networks.
  
  When the first number is 128 to 191 - nnn.nnn.xxx.xxx (ex. 172.16.xxx.xxx)
  These are known as "Class B" networks.
  
  When the first number is 192 to 223 - nnn.nnn.nnn.xxx (ex. 192.168.1.xxx)
  These are known as "Class C" networks.
  
  When the first number is 224 to 239 - The address is used for multi-casting.
  
  When the first number is 240 to 255 - The address is "experimental".
  
  Multicast & Experimental addresses are beyond the scope of this article. However, because IPv4 does not treat them the same way as other addresses they should not be used.
  
  The network portion specifies a network; the host portion specifies an individual device on a network.

For any given network:

• The range of all possible host portion numbers gives the Address Range.
  (ex. 172.16.xxx.xxx the range is 172.16.0.0 to 172.16.255.255)
• The lowest possible address is the Network Address.
  (ex. 172.16.xxx.xxx the network address is 172.16.0.0)
  This address is used by devices to specify the network itself, and cannot be assigned to any device.
• The highest possible address is the Broadcast Address.
  (ex. 172.16.xxx.xxx the broadcast address is 172.16.255.255)
  This address is used when a packet is meant for all devices on a specific network, and cannot be assigned to any device.
• The remaining numbers in the range are the Host Range.
  (ex. 172.16.xxx.xxx the host range is 172.16.0.1 to 172.16.255.254)
  These are the numbers you can assign to computers, printers, and other devices.
  Host Addresses are individual addresses within this range.

2. connect the two computers together.

• To connect with a Crossover cable, simply plug an end of the cable into the Ethernet Port of each computer.
• To connect with a Hub or Switch, use two straight through cables to connect each computer to the switch or hub.
• See "Things you will need" section for more information on "Straight Through" -vs- "Cross-Over" Cables.

3. Configure the computers for networking. Go to internet options (this varies depending on the Operating System), and go to the dialog box that lets you change the TCP/IP protocol. Change the radio buttons from "Obtain from DHCP server automatically" to "Use the following IP address:".

• Give each computer a different address from the host range. Do not use the network address or the broadcast address.
• Leave the "Default Gateway" and "DNS server" fields blank.
• For the subnet mask, use the following:
  
  Class "A" Networks
  When the first number is 0 to 127
  The Mask is - 255.0.0.0
  
  Class "B" Networks
  When the first number is 128 to 191
  The Mask is - 255.255.0.0
  
  Class "C" Networks
  When the first number is 192 to 223
  The Mask is - 255.255.255.0
  
  IPv4 originally used the first number (ex. 192) to determine which part of the address is network and which part is host based on the address class. However, the advent of subnetting and nonclassful networking made it necessary to provide a mask because other ways of dividing the address into network and host portions are now possible.(More information in the Important Notes section.)

4. Verify connectivity. The simplest way to do this is with Ping. Bring up MS-DOS or the equivalent on other OS's, (In Windows open the command prompt which is located in the Start Menu - Accessories - Command Prompt) and type in: "ping [insert IP address of the other computer here] (ex. 192.168.1.1). If you cannot reach the other computers address, read over the steps again or contact a professional.

GOOD LUCK , I HOPE IT WILL HELP YOU.