Internet Protocol (IP) Address Interview Preparation Guide

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IP addresses are used to transfer information across the internet. If you type www.ibm.com into your browser, your computer resolves this friendly name into the equivalent IP Address of IBM’s webserver, and then retrieves their homepage using this IP address. While you are connected to the internet, you are assigned a unique IP address as well, which is shown at the top of this page. IP addresses are defined in the TCP/IP protocol family, which is the basic technical foundation of the internet.

The IP address shown on this site is always the correct internet address, which is seen by all webservers and hosts you visit. If your computer has a network card and is connected to other PCs at your site, then you have a second, local IP address which is different from the internet address of your DUN connection or your firewall or router, which substitute all internal addresses with a true internet IP address.

DNS stands for domain name service. It can be thought of as a large, distributed database, containing all internet domain names and hosts, such as www.mywebsite.com. The reason for using DNS names instead of IP addresses is simple: meaningful names are much easier to deal with by human beings than numbers, such 212.202.126.70 If you are using a Dialin or DSL connection to your provider, the DNS name shown is probably a somewhat cryptic name, which is used by your provider internally to organize and manage the numerous dialin ports.

Domain names are like trademarks: competitive names are valuable and much sought-after. They are basically given on a first-come first-serve basis by international organizations, such as ICANN, DENIC, and several local organizations responsible for one ore more top level domains, such as .com, .gov, .de, .info and so on. The mechanism to query the current, registered owner of a domain name is called WHOIS. Type in any domain name, such as www.globalguideline.com or any ip address to find out the legitimate owner.

In an attempt to fight spam, several organizations began building black lists in order to ban domain names or IP address ranges that were accursed to be involved in unwanted practices. Many large organizations use these block lists to filter incoming emails. If you notice that some of your emails consistently fail to reach specific recipients and you verified the email address for validity, check if your IP address is blocked and, if so, talk to your provider to rectify the situation. If this happens more than once, get yourself another, better provider.

Most people think of the internet as surfing, downloading and mail, period. They simply use their internet connection to access some outside services. But imagine what could be done if you reverse the direction: Accessing your computer (or network) from the outside world will eventually open up a whole set of exciting new possibilities, like sharing data with customers and suppliers, IP telephony, video conferencing, remote control or working abroad, monitoring and controlling your premises and much more. All of these services need to access your computer or firewall by using its internet IP address as a doorway. Even if you don’t become excited about these possibilities, rest assured that many others are! Marketing companies geolocate your ip address, track your browsing habits with cookies or spyware and hackers are running robots to locate unsecured PCs. So this website will be dedicated to everything that could be done by accessing this doorway (your IP address), including important questions of security and privacy that will inevitably arise. If this sounds interesting, stay tuned!

An IP Address is a unique number used to identify a computer or a network device in the network or on the Internet. An IP Address looks like the following,xxx.xxx.xxx.xxx where x is a decimal representation of the equivalent Hexadecimal value. As you can see, there are 4 Octets split by three DOTS. This way of representing an IP address is called DOT Notation. An IP Address comprises of 2 parts. A Network ID and a Host ID. In simple words, its like the Street Address and the Door Number, where Street Address is your Network ID and the Door number is the unique host ID.

Well, thats where there comes in a new component called Subnet Mask which allows systems to differentiate between Host ID and the Network ID.

A Subnet Mask is an address mask that allows, systems to differentiate between the Network ID from that that of the Host Ids in a IP Address. This is represented very much as how an Ip address is represented.

As the Internet is flooded with more and more networks and computers, the system is now slowly running out of available addresses to fit in more networks or computers. For this reason, IPV6 is being designed. This is a new version of the IP protocol addressing method (V6 is Version 6) which is to slowly and steadily replace the existing IPV4 (V4 is version 4).

A Default Gateway is an address to which all the packets to which there is no known Route is available is been sent. In otherwords, if the system doesn't know where to send a set of packets, it will forward it to this address which then takes care of routing to appropriate destinations.

A connection Gateway is very much like a Default Gateway except for the fact that this address is the one where any packets that needs to be sent out on the Internet is been routed to. In other words, this is the address that communicates on the Internet and hence known to the Internet.

Every Operating System has its own way of showing the IP Address. In windows,
1. Click Start – Programs – Accessories – Command Prompt.
2. Type ipconfig and press Enter. This will show the IP Address, Subnet Mask and the Default Gateway. For detailed information, type ipconfig /all and press Enter. In Unix/Linux/Solaris Open a Terminal window and type ifconfig. NOTE: This requires you to have sufficient priviledges to execute the command.

A private IP Address is the one, which is not recognised on the Internet. This is mostly used to connect different devices locally on a small network or even in huge networks. These devices cannot directly participate on the Internet for the simple reason that they are recognised. This is where devices like Router comes into picture where it translates all the packets from these Private devices into the Public IP Addresses that is being assigned and forwards to the Internet and exactly does the reverse for the incoming packets on the Public IP to give it back to the private devices. This process of translation is called Network Address Translation and the process of forwarding packets from various different networks to different other networks is called Routing.

Yes, there is one as follows:
(10.0.0.0/8) –
10.0.0.0 to 10.255.255.255
172.16.0.0 to 172.31.255.255
192.16.0.0./16: 192.168.0.0. to 192.168.255.255

A loopback address is the one, which normally used internally by the system to point to itself. This is different from another Public or Private IP Address. This is mostly used to call the local system and for troubleshooting purposes. The default Loopback IP Address is 127.0.0.1

On the other hand, Public IP is the face of any network device or a computer on the Internet. This address is the valid address normally assigned by your Internet Service Provider to your network or your computer.

Well, there is no actual difference between these addresses except for the fact that a set of address are reserved for private use and can be used by anyone to use locally on their network. Unlike, the Public IP Address are assigned by your ISP and normally comes at a cost (Home users may not pay for this but are hidden in your Internet charges). Additional Public Address can be purchased, in other words, leased from the ISPs to host servers of your own on the Internet.

There are 2 ways that any Network device will get its IP Address. One is manual entry by users / administrators while the other is automatic called DHCP. A DHCP server in the network (locally) or at your ISP (Public) does this job. Normally, most if not all computers and network devices are setup to look for a DHCP server and obtain IP Address.

A firewall is as much as the huge walls of a Fort to block enemies coming into the territory. These are devices or Software which deny access to your computer from anything external. It stops hackers, intruders and other malicious evils from accessing your computer and take any critical information like Bank Account Detials, Credit Card details, Identification Information or even your Business critical information. It is highly advisable to have a Firewall device or a simple software loaded on your computer from these evils. Apart from using firewall, one has to ensure that a proper antivirus software
/ mantispyware software is installed and properly run on the computers to ensure absolute security on the Internet, failing which you always vulnerable to attacks from the Internet.

The IPID is the Identification field of the IP protocol packet header which a;long with the source address uniquely identifies the packet. The IPID is used to reassemble the packet should it be fragmented. Every fragement of the packet will then have the same IPID for the destination device identify them all to be a simgle packet.

The IPID is primarily used in the Idle Port Scanning by a hacker where he spoofs a victims IP address to then use it to scan a target network or system. Various Operating Systems generate these IPIDs in different ways.

Static IP is also called as permanent address assigned to each device in a network, whereas Dynamic IP, a temporary address assigned to the device via DHCP software. IP address assigned to your service by your cable or DSL Internet provider is typically dynamic IP. In routers and operating systems, the default configuration for clients is dynamic IP

IP address or Internet Protocol address is the address of a device attached to an IP network (TCP/IP network). It is a must for every client, server and network device to have a unique IP address for each network connection (network interface). Every IP packet contains a source IP address and a destination IP address. As a device moves from one network to another, its IP address changes.

Private address: these IP addresses are used exclusively within a private network and not for public to see.

Public Address: these are registered IP addresses used for public.

Each IP address has a network address and a host address. IP addresses are expressed in four sets of three numbers, separated with dots. Each set is called as an octet because when converted to binary; it denotes eight binary.

Network Address Translation acts as an agent between the Internet and a local network. It is a dynamic method which is used to minimize Internet connectivity needs. Network address translation describes the rewriting of the Internet Protocol (IP) addresses of data packets so that multiple transmissions require only one IP address.