Internet Protocol (IP) Address Interview Questions & Answers

Download PDF

ipconfig

A Domain Name system is used to convert the names of the website on the internet to IP addresses. The domain names for each IP addresses are stored in a database that is distributed across different servers. A domain name space consists of a tree of domain names. The tree has zones. Zones consist of a collection of connected nodes. These nodes are served by a name server. A domain name is usually in the form of mydomain.com. Here, .com is the top level domain. Where as mydomain is the sub domain or subdivision. A host name is a domain name that has one or more IP addresses associated with it.

When a source sends a packet to a destination, this packet has a specific path or route it follows. Different routing protocols are used to find the shortest path to the destination. The protocols maintain routing tables. Routing tables consist of a set of rules used to determine where these packets will travel. When a packet is received, a network device examines the packet and matches it to the routing table entry providing the best match for its destination. The packet keeps hopping until it reaches its destination.

Each IP address is 32 bit long. In human language the IP addresses are written in dotted decimal notation. These are then converted to binary by the computer. Each IP address has two parts: Network identifier or a network ID and host ID. The current internet protocol standard is IPV4. The IP addresses are divided into three classes: a class A network, a class B network, and a class C network. Class A being the largest. The four digit numbers in an IPV4 address, each network of class A will have different first number, and then its network will be addressed by the rest of the three numbers, or three bytes. The IP addresses identify a machine to deliver packets and load web pages.

Routing protocol specifies how the routers communicate, disseminating the information which enables the routers to be selected between two nodes in a network.

Routing protocol interacts and informs the hardware that is needed to transmit the data between transmitter and the receiver for transmission over network.

Address Resolution Protocol ARP, is responsible for mapping an IP address to its corresponding physical network address. It is mostly seen on Ethernet network.

MTU specifies the largest amount of data that can be transferred across a network.

Domain Name server or DNS is used to resolve names into IP addresses. When a web address is entered into the browser, the DNS client sends a request to the DNS server to find the corresponding IP address for the name. The DNS server receives this request and searches for the corresponding IP address in the database. If at this point the resolution fails, this server sends this request to the parent server. The request keeps going up the hierarchy to the parent servers or the closest authoritative of the DNS server to resolve the address. If the request times out an error is retuned to the client. If the server is able to resolve the name requested, it passes the information back to the client. The next request sent by the client is to request for a web page for the IP address.

IP multicast technology reduces traffic by sending stream of information to many recipients at one go. Video conferencing, stock quotas are the examples based on IP multicast.

A public IP address allows equipment accessible to everyone on the internet. A private IP address is for private use within the network and allows many more PCs to be connected. If you are using a private IP and wants VOIP, you need to change to a public IP address.

Subnet adds one level to the way IP address is represented. It logically organizes the network. For instance, it can logically group computers belongs to the finance department.

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.

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.

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.

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

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.

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.

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.

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.

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.

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

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 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.

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 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.