Description Of The Dhcp Computer Science Essay

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DHCP or Dynamic Host Configuration Protocol is a protocol client/server that automatically provides an IP Address or Internet Protocol Address to DHCP clients with its IP address. Default gateway and Subnet mask are the other associated configuration information which are also provided by the DHCP server automatically to the client . DHCP shares many implementation details with Bootstrap Protocol (BOOTP) .Bootp is a host configuration protocol from which the DHCP Dynamic Host Configuration Protocol is developed. In other words DHCP is the improved version of BOOTP

How DHCP or Dynamic Host Configuration Protocol Works

A DHCP server is a computer or device in which the DHCP services are installed. DHCP server distribute and renew Internet Protocol (IP) addresses and other configuration information such as default gateway and Subnet mask on a network information to a DHCP client through the DHCP conversation which is exchange of a sequence of messages. DHCP conversation is also known as the or the DHCP transaction. In case if DHCP server and DHCP clients are on different subnets, a DHCP relay agent is used to assist the DHCP conversation or DHCP transaction

The DHCP client broadcasts a message to find the local DHCP server when the client computer or device is switched on which is called DHCPDISCOVER

DHCP server that receives a clients DHCPDISCOVER message and can examine the information, sends a message known as DHCPOFFER to the client with a set of parameters

The client receives one or more DHCPOFFERs, and decides which offer to accept. Then client send the DHCPREQUEST to the DHCP server from which the DHCPOFFER is accepted by the client

And lastly the server sends the DHCPACK to the client with full set of configurations parameters, confirming the client that it got the DHCP REQUEST and provide the full set of required information, The "ACK" part of DHCPACK name comes from acknowledgement which is to ensure the DHCPREEQUEST is completed

If a client requested (DHCPREEQUEST) an address which is that is incorrect or expired the server send a message know as DHCPNAK to the client to inform the request is rejected. The NACK of DHCPNACK name comes from negative acknowledgement which is to ensure the DHCPREEQUEST is rejected

If the client get an offered address, and subsequently discovered that is address is already being used in the network. Client sends the DHCPDECLINE to the server to inform that the address is already in use

When a client no longer needs to use the automatically or dynamically assin5ged address, It sould send a DHCPRELEASE message to inform the server that this address in not being used anymore

If client already had the IP address but still need some configuration information. The DHCPINFORM message will serve the task

Core components of DHCP

Following are the four main components for DHCP or Dynamic Host Configuration Protocol

Internet Protocol

Default gateway

Subnet Mask

Domain Name Server

IP address

An unique` number assigned to every computer or device Network which usses TCP/IP protocol usses routing of messages based on IP address of the source and destination of the computer or devices The IP address is a numeric 32-bit in fore separated by dots and contains three digits in each periods. The range of each numbers can be 0 to 255. For example the IP address can be written as To identify a particular network and a host on that network, the four numbers in IP addresses are used in different ways

Within a single network unique addresses can be used for each computer and devices connecting to the network. Duplicating of IP Address on more than one computers or devices can create many issues in the network. To connect the private network to the internet, Internet Addresses (Registered IP Addresses) are used to avoid duplications of IP address

IP address is a group of 4 numbers through which computer are able to send and receive data over the internet connection and also ensure that the requested data will reach the internet connection properly. Without Internet protocol data transfer (sending and receiving data) between source and destination over the Internet would not be possible

Subnet mask

An IP address is a combination of 2 components, Host address (host ID) and a Network Address (Network ID) The role of the Subnet mask Is to separates the IP address into the network address and the host address .Thee role of the subnet mask is also divided Host address into 2 parts which are Host address and subnet which will finally result the separation of IP address as Network address - Subnet - Host address

Default Gateway

The computer have a network setting called Default Gateway that assigns the Internet Protocol Address to the Computers or a routers to which the traffic of the network to be send when the sending computer is not the same as the subnet on the network. The computer is on what subnet is determined by the net mask and IP address of the computer

Domain Name Server

Domain name server is the protocol which convert or translate the domain name to IP address because almost everything on internet is based on IP addresses .For example Domain name "" is alphabetical and easy to remember but it has to be translated to the IP Address to access the domain over the internet

Strengths of DHCP

When a computer or device is connected to the network it is necessary for the device to have an Internet protocol (IP) address which is a unique address of the device or computer on the network. Strength of the DHCP in this case is the DHCP will automatically and dynamically assigned the IP address to the computer or device which is connected and will be ready to communicate to the other devices on the network. All the IP addresses which are assigned to the devices on the network are stored in the DHCP service so it is not important to remember all the assigned IP Address to each of the devices. If the computer or device is relocated to the other subnet the DHCP server will automatically assign an IP address to the device. If the device or computer is not in used by the network or the computer is offline, DHCP has the capability to release the particular IP address and assigned that IP address to another computer or device on the network. Duplication of IP address (assigning same IP address to more than one device or computer) is eliminated because DHCP automatically keep tracks of the IP address which bare already assigned to each computers or devices. DHCP reduces network administration

Weaknesses of DHCP

If the computer on the network i is a DNS AND WINS Server each instance the internet protocol changes take place, it will work according to Lease If a DHCP client request an IP Address and if the DHCP Server is not able to contact it will automatically assign a APIPA Address (the computer will automatically assigned the IP address on its own which can be duplicated from the other computers on the network

The computer name does not modify when the computer get a new IP address automatically. The Domain Name System (DNS) name is linked with the Internet Protocol address and for that reason do change. This only presents a problem if other clients try to communicate with the computer by its DNS name.

One of the weaknesses is DHCP is not user friendly to the non-computer devices. A connection cannot be established without including setting some of the variables. And port forwarding no longer be reasonable, because devices can be assigned different IP's each instance they are connected to the network

DHCP can be a serious security risk if a rogue DHCP server is introduced to the network. A rogue server isn't under control of administration, and can assigned IP addresses to devices connecting to the network. If a computer connects to the rogue DHCP, Automatically IP address will be assigned and will be able to communicate to a network so information sent over that connection can be intercepted which will violate user privacy and network security

Relationship of Dynamic Host Configuration Protocol (DHCP) with Network Management

Server is a computer which has DHCP functions installed so the so the server acts as a DHCP server. The DHCP server help in managing the IP Address by assigning the Unique numbers called IP adresses to the computer automatically and dynamically which are connected to the network. All the available IP addresses are stored in the IP address pool of DHCP server. As a DHCP client connected to the network or switched on, DHCP server will automatically assign the IP Address from the IP Address pool and other required additional configuration information (Subnet Mask, Default gateway) to DHCP client. As soon as the DHCP in disconnected from the network and IP Address is no longer in used .DHCP server send the unused IP Address to the Pool which can be used by the other devices.

Automatic IP Address assigning in DHCP is very useful in big networks because assigning a static IP Address to all the computer and devices in a big network can be troublesome and hard to manage

DEVICES (Adnan Raza TP023297)


A router is a computer that runs software that figures how a packet should be forwarded on the route to its destination. A router works at the internet layer of TCP/IP layer, and connects to at least two networks (Leiden, C., Wilensky, M., 2009).

Most of the routers located in homes and offices help to send web, email, and other Internet messages from local area network through cable or Digital Subscriber Line (DSL) modem to Internet Service Provider (ISP). ISP then send routed messages out to the Internet. Normal Local Area Network of offices or homes and the ISP are connected by combination of modem and router. Router and switch are similar but the difference is router "route" the packets to other networks. The routers are connected on the gateway for the networks and connect at least two or more networks together. The most common use of router is to connect a Local Area network (LAN) with Wide Area Network (WAN) .A router not only helps to connect the Internet but also help to protect the LAN from Internet.

Router has address translation and filtering capabilities which differ itself and make it more intelligent from other similar devices like switches and hubs. The picture below is showing how a router connects a Local Area Network (LAN) to Wide Area Network) WAN.

how does a router work

(LAD Enterprises, 2007)

As the picture shows that how a router does help the computers to get connected to each other. As a switch create a LAN connection allowing them to do data sharing and printer sharing. Router also works as a gateway for the computers which are connected to allowing all the computers to get connected to internet to help in joining LAN with WAN.

How Router works

Router is the central component in connecting network devices and computers together, which allow them to share and access internet connection at a very high speed. It also helps in organizing all the devices in a network so that they can communicate and share information with each other. A router has a combined feature of a switch, which control and organise data flow between the computers and networks devices. Data sharing can also be done using switches but switches cannot provide internet access.

The router connects two networks home LAN and the Internet passing information from one to the other. It also firmly decides how the data is transferred in most efficient way. The router has two main jobs and these are:

(CISCO, 2012)

1. To make sure the information does not travel where it is not supposed to be.

2. To make sure the information is travelled to its actual destination.

Routers also help in security of the network by preventing outside users from accessing user's private data. This security is very important because the internet connection is always on and allows hackers to attack easily.

Strength and weaknesses of Router

Strength of Router

1. Routers limit the collision domain.

2. Routers functions on both Local Area Network (LAN) and Wide Area Network (WAN)

3. Routers connect different type of architectures and media.

4. Routers determines best route for the data to reach the final destination.

5. Routers can filter the broadcasts.

6. Routers divide the broadcast domains.

7. Router provides security to network using Access Control Lists (ACL) and Network Address Translation (NAT).

8. New router technologies help connecting wirelessly to the network.

Weaknesses of Router

1. Routers are expensive than other related devices like Bridges, Hubs and Switches.

2. Routers just work with routable protocols.

3. Bandwidth is consumed by routing updates.

4. Latency is increased due to greater percentage of packets filtering.

5. Router cannot identify which system is server and which is client in the LAN.

6. Routers are Software based due to which it is slower than switches.

7. If Routers are not configured properly can lead to data lost.

8. Router need configuration and some time it needs professional consultations.

Core components of the Router

The four main components of routers are Input ports, Output Ports, a switching Fabric and the routing processor.

• Input port:

Input ports have two functions.

1. It helps to carries out data link layer encapsulation.

2. To determine its destination port, it also has the intelligence to look up an incoming packet's destination address in its forwarding table.

• Output port:

Before transmitting packets to out link output ports store the packets. To support priorities and guarantees output port can implement sophisticated scheduling algorithms, not only input ports but output ports are also needed to support encapsulation of the data link layer, and different types of high-level protocols

• Switching Fabric:

Many different techniques can help to implement switching fabric. Busses, crossbars, and shared memories are the most common switch fabric technologies. The simplest switch fabric is a bus and it links all the input and output ports.

• Routing processor:

Forwarding table is compute by the routing processor, which apply routing protocols and execute software to manage and configure router. Routing processor helps to handle packet, if any packet's destination address cannot be found in the forwarding table in the line card.

Router can store data in different location for example:

• Read-Only Memory (ROM)

• Flash

• Non-Volatile RAM (NVRAM)

• Random-Access Memory (RAM)


Router's Power on diagnostic, operating system and bootstrap startup programs are stored on Read Only Memory (ROM) and pluggable chips are removed and replace from the main board for the ROM up gradations.

Flash Memory:

Flash memory is use to store operating system images. It is a reprogrammable and erasable ROM. Software upgrades can be done without even replacing the hardware chips. This flash memory content does not discard even when the router is switch off or restarted.


RAM stores the information which is related to operations such as routing running configuration and routing table. It also provides packet buffering and caching capabilities. The content of router's RAM is lost when it gets restarted or switched off.


Router configurations file related to startup are stored in Nonvolatile RAM (NVRAM) even though the router is off or restarted these information are store and does not goes away, this is where the startup configuration files are store and maintained.

Router in managing Network

Router is the best and the easiest device for creating or maintain networks as it gives around four wired LAN connection as it has only four LAN ports and 254 wireless connections depending on router functionality. More LAN computer can be added by just connecting external switches to it. Router automatically share internet connection to all the computer which are connected to it, not only internet but other devices like printers, LAN storage devices, and file sharing can be done using routers. They also protect the LAN as they have an inbuilt firewall making it a safest way to maintain network. Upgrading and installation can be done in minutes so it is cheap and faster.

Some of the key functions of Routers which help in managing network are:

1. DHCP server

Dynamic Host Configuration Protocol (DHCP) server is an inbuilt function of a router which gives Internet Protocol (IP) addresses to the devices as soon as it connected to the router. Using DHCP the router manages the network and help in providing internet sharing to all the devices connected and sharing other resources like printer, files and network programs without even having a physical server.

2. Switch

Almost all the router comes with build in four LAN ports switch which helps to connect four devices and ports can be increased by simply connecting external switches to the router. Small network with four computers do not really need switches but more than four computers can be supported by just connecting external switches.

3. Hardware firewall

Firewall in router helps to prevent attacks to the computer on the Local Area Network from the Internet, so the external users on the internet cannot access the resources like file and printers from the remote area without permission.

4. Internet sharing

Router helps in connecting to the internet and shares the internet connection among all the users connected. So that all the system which are connected to the router can easily access the internet without any type of configuration. Even internet access control can be done on the bases of many criteria like working hours and job timings.

5. Wireless

Most of the new routers come with the wireless technology which means the wireless devices can easily get connected to the router without any physical cables and use the internet connection or resources which are available on the Local Area Network. Working on wireless network make it easier to manage network as no cabling is require and computer with the wireless LAN card can easily be connected to it. One normal wireless router can support up to 254 wireless clients by giving IP address. The range of the wireless can be extended by using access points.


How does the combination of Router, DHCP protocol and Client/Server architecture helps in network management.

Router is a physical device which is built-in service or function called Dynamic Host Configuration Protocol (DHCP) server which gives each and every devices a unique address which is called Internet Protocol (IP) addresses. This helps all the devices to communicate with each other and to share resources. As the router cannot differentiate the difference between a client and a server so that the client server architectures is implemented and it define the server and client. The DHCP server can also be used in a server when it is done in huge network. Client server architecture defines where the data will be stored and how the group policies and access control list can be implemented so that one user from different department cannot access other departments.