Network topology of Holku Industries

Introduction

Holku Industries is a medium sized company, currently with 200 hosts distributed into four departments. The company has a Single Private Class B address. (See figure 1.1). With a moderate budget, the design should be cost effective using the least amount as possible. (See section 3.1 to 3.4)

This can also be written as: 172.25.0.0/16

Devices and Network media used

The project has been designed with the minimal amount of equipment used to achieve higher cost effectiveness while meeting the business requirement. Figure 2.0.1 shows the summary of equipment used for the project.

WIC-2T Modulated 2621XM Router

Each router is connected to two switched through the Fast Ethernet port (Fa). The router is modulated with a WIC-2T module which allows it to connect with another router through the Serial port RS-232(Se).

2950-24 Switch

The main advantage with a switch is that it can control the traffic flow in network causing less congestion by sending packets to designated devices only. Therefore a switch has been chosen instead a hub since a hub is unable to cope with the traffic produced by the existing 200 host. The 2950-24 switch has been chosen for the design and will be explained in section 3.0.1.

Copper Straight-through and Cross-over cables

These cables are the physical connection between devices allowing them to communicate with each other. The Copper straight-through cable connects to devices such as 'PC's to Switches' and 'Switches to Routers'. The Straight-through cables will connected to the Fas on each device. However, the Cross-over cable will only be used to connect 'Switches to Switches' together on the Ethernet ports.

Serial DCE Cable

The Serial DCE cable will only be used for the connection between the 2 routers which enables a WAN link. These are connected through the Ses on each router. We did not use the DTE cable to connect to routers mainly because an internet connection was not necessary. If an internet connection was needed, then a DTE cable would be ideal for the connection.

Proposed Solution

To meet the requirements, we have subnetted the single IP into five separate subnetworks, Sales, Manufacturing, Warehouse, Admin and WAN links (Wide Area Network).

Sales Department

In the sale department, the host requirement is 75 hosts. The closest, yet meets the minimum requirement we can have on a single subnetwork is 128 hosts. Therefore this department will be assigned with an IP address network of:

This can also be written as: 172.25.0.0/25.

This is known as the first subnetwork of the 172.25.0.0 network.

Manufacturing department

In the manufacturing department, they have a host requirement of 65 hosts. Same as the sales department, the closest we can meet the host requirement on a single subnet is 128 hosts. This department will be assigned an IP address of:

This can also be written as: 172.25.0.128/25

This is known as the second subnetwork of the 172.25.0.0 network.

Warehouse department

In the Warehouse department, they currently have a host requirement of 40 hosts. The closest host availability that can meet this requirement on a single subnet is 64 hosts. Therefore the IP address we can assign the department is:

This can also be written as: 172.25.1.0/26

This is known as the first subnetwork of the 172.25.1.0 network

Admin department

In the Admin department, they need to have a minimum requirement of 20 hosts. The closest host availability that can meet this requirement on a single subnetwork is 32 hosts. The IP address that we can assign to this department is:

This can also be written as: 172.25.1.64/27

This is known as the second subnetwork of the 172.25.1.0 network.

WAN Links

The WAN links will interconnect the routers connecting to the other department which only needs 2 hosts. We will need a single subnetwork with 4 hosts that meet this requirement. Therefore the IP address we can assign this network is:

This can also be written as: 172.25.1.96/30

This is also known as the third subnetwork of the 172.25.1.0 network.

Configurations

The "Network Address.xlsx" file shows all the available address for each subnetwork for every individual device needed.

IP address Allocation

Each device apart from the switches will be assigned an IP Address. The first host in each subnet will be used as a Default Gateway Address which connects to the routers. However, a Default Gateway will not be needed in the connection between the routers as it is a Point to Point Connection.

'Router A' and 'Router B' Configuration

IP addresses will be assigned in Fa0/0 and Fa0/1 and in Se0/0. The IP address in the Fa will be used as the Default Gateway for each of the Subnet.

Se0/0 is used for the WAN links, therefore an IP address will be assigned here. A clock rate will be set to '64000' on 'Router A Se 0/0. The routing table will be configured dynamically using RIP Routing (Version 2) passing all unknown routes to 'Router B' and vice versa on 'Router A'. See "Network address.xlsx" file for IP addresses.

The Good and the Bad

There will be advantages and disadvantages with the proposed solutions. In such cases there will be alternatives to designing the network that meets the company requirements. Figure 3.6.1 shows a list of all the good and bad points as to why this design will be suitable for the company.

Possible solutions

There are a certain number of ways to design a network apart from the solution designed. We will list the possible solution and show the advantages and disadvantages to these possible solutions.

Solution 1

Rather than dividing the network into five subnetworks, we can use a single network and assign IP addresses to all devices available. In this situation, it would cut down costs on purchasing new devices (e.g. routers, switches, etc.). Although fewer budgets will be used to purchase new devices, this would slow down the broadcast traffic causing less productivity.

Another disadvantage to this solution is the security issue that can affect the network. An example where any device on the network can be infected with a virus and it cannot be isolated quick enough to prevent it from spreading onto other devices on the network. Apart from virus attacks, confidential information about the company may be disclosed to certain employees who should not have access to the information. See figure 4.1.1.

Solution 2

Another solution would just simply divide the network into 5 subnetworks. The difference in this is that we would be dividing the network with a network perspective and not the host perspective. It would work in almost exactly the same as the proposed solution except that there will be wasted addresses. This means there will be at least 16,300 hosts wasted on each subnetwork. This again will slow down the broadcast traffic within each subnetwork causing less productivity in each department.

Another issue of the wasted address allocation is that the routing table in the router will become huge causing large consumption of memory and requiring more time for the CPU processer to search through. See figure 4.2.1.

IP summarisation

The Summarisation of the Network IP will be: 172.25.0.0/23

Topology of network.

Purpose of the OSI Model

The Open System Interconnection (OSI) model is used to describe the layer of communications and computer network protocol design. It divides the network architecture into 7 layers which provides a service to the layer above and receives services from the layer below. Each layer, top to bottom, are named Application, Presentation, Session, Transport, Network, Data Link and the Physical layer. The OSI is a reference that shows how data travels through each layer when it is sent from a device over a network.

Physical Layer

At layer 1 (Physical layer) of the OSI model, the main roles of this layer are:

  • The responsibility of the physical connection between devices.
  • Allowing the start and end of a communication in a connection medium.
  • Signalling and Encoding Bits for the Media.

Devices in this layer:

  • Network Interface Cards
  • Transceivers
  • Repeaters
  • Hubs
  • Multi Station Access units

Data Link Layer

At Layer 2 (Data Link Layer) of the OSI Model, it is divided into 2 sub-layers, the Logical Link Control (LLC) and the Media Access Control (MAC). The Data Link Layer prepares the packets from the Network Layer to be placed on the Physical media.

(Cisco networking academy, CCNA Exploration 4.0, Network Fundamentals)

Network Layer

The main role of the Network Layer allows it to carry any sort of data from 1 host to another. This is where data encapsulated into packets where the destination address lies inside the field of the packet header.

(Cisco networking academy, CCNA Exploration 4.0, Network Fundamentals)

Transport Layer

The Transport layer divides the application data into segments. It adds a header with information to assemble the segments back into application data once it arrives at the destination. It is responsible for the delivery of the data to the correct application on the destination host.

(Cisco networking academy, CCNA Exploration 4.0, Network Fundamentals)

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