Network Design and Troubleshooting Project for alm.co.uk

Desklib provides solved assignments and past papers to help students succeed.

NETWORK DESIGN AND
TROUBLESHOOTING

Table of Contents
Introduction................................................................................................................................3
Knowledge and Understanding..................................................................................................4
Application and Analysis...........................................................................................................5
Evaluation of Different Technologies Used...............................................................................7
Design, Implementation and Testing.........................................................................................8
VLAN Configuration.................................................................................................................8
Conclusion................................................................................................................................18
References................................................................................................................................19
Table of Figure
Figure 1: VLAN creation and configuration..............................................................................9
Figure 2: Showing the created VLANs for all 4 departments..................................................10
Figure 3: Showing the VTP configuration...............................................................................10
Figure 4: Trunk port configuration..........................................................................................11
Figure 5: Configuring layer 2 switch port g0/1-2 as trunk.......................................................12
Figure 6: Showing switch port in trunk mode..........................................................................12
Figure 7: DHCP configuration according to the subnetting for all four departments..............13
Figure 8: DHCP configuration and Assignment......................................................................14
Figure 9: Intra-VLAN connectivity.........................................................................................14
Figure 10: Access list configuration for VLAN 10..................................................................15
Figure 11: Access list configuration for VLAN 30..................................................................15
Figure 12: Creation and configuration of DNS server.............................................................16
Figure 13: Accessing DNS server............................................................................................17

Introduction
This assignment provides a case study based on network infrastructure design and
implementation which is to be analysed and then created and configured, henceforth. The
topic given just assesses and enhances our ability to design network infrastructures and
troubleshoot them accordingly. According to the given scenario, we need to implement a
network infrastructure for a client company ‘alm.co.uk’. This network needs to have four
separate departments, the users of which cannot access each other’s departments. The
network also contains four servers namely, web, email, DNS and file server which are shared
among all the users. These servers are provided for access to all the departments.
Requirements of each department along with their access rules are mentioned below in the
table provided:
Dept. Devices Access Rules
1 48 Computers one printer Users cannot access any other department
2 18 Computers one printer Users cannot access any other department
3 11 Computers one printer Users cannot access any other department
4 68 Computers one printer Users cannot access any other department
Table 1: workstation and server distribution and requirements
We definitely need to ensure scalability, security and availability of the entire network
implementation. Network also contains the inclusion of wireless devices such as smartphone
to access internet. This wireless network would be using an IP address of 10.11.12.0/24 and
the entire company would be using the private IP address of 192.168.168.0/24 within the
LAN.
For the entire above-mentioned scenario, an in-depth analysis and investigation was carried
out to evaluate a suitable network model and its components for the designing of the network
infrastructure, keeping in mind the provisions of scalability, availability and security. Here
we are going to use a ‘Star modified hierarchical network topology’ also known as
‘Collapsed core network model’.
 Star topology is a network topology where all the nodes of the network are connected
to a central point, be it a hub or a switch.
 Hierarchical topology is a network topology which is implemented when we have to
interconnect numerous groups which are located on separate layers and as a result,
form a larger network.
Thus, star modified hierarchical network topology is a combination of both of the above-
mentioned topologies.
 Collapsed core model for network design and implementation is a model in which two
layers namely, distribution layer and core layer are collapsed and combined into a

single layer and their functions are performed and implemented by a single device.
This modular approach ensures maximum network availability, performance and
security along with the ability to scale the network according to the requirement. This
approach is also followed as it makes the network highly cost-efficient which is one
of the most significant factors to be considered while designing and implementing a
network infrastructure. Below shown is a general collapsed network model where the
functionalities of core layer and distribution layer are implemented through multilayer
switches.
Thus, the purpose of entire report is to analyse the given scenario and demonstrate the
followed effective approach for the network design along with the description of the
components used including the reasons of their selection and the inter-relationship
between them.
Knowledge and Understanding
The given assignment proves to be really useful in terms of enhancing the knowledge of
network design and implementation. Network infrastructure includes all the hardware and
software requirements of the entire network that would be necessary for proper and
successful connectivity and operations of the network. And the process of network design
includes a looping process of planning and implementing a suitable topological design,
network realization and network synthesis process. If we talk about the above-mentioned case
study, one of the effective approaches to implement this is to analyse its functional and non-
functional requirements. A comprehensive, detailed and sensible collection of both functional
and non-functional requirements contributes to the successful designing of the entire network.

The functional requirements while implementing a network infrastructure include the analysis
of the required network’s recommended performance, use and the environment suitable for it.
It includes the entire work-flow, connectivity and operations going on in the entire network.
Functional requirements describe what the network is intended to do, it describes the entire
operational specification of the network. It specifies the behaviour of the network.
The non-functional requirements specify how the network is designed; it looks after the
design specifications of the network. It specifies how the entire network should behave; it
constitutes the quality attributes of the network. Non-functional requirements constitute
capacity, availability, reliability, security, scalability and maintainability, etc of the entire
network.
Thus, functional requirements constitute the behaviour and operations of the network while
non-functional requirements specify the quality characteristics of the network. These are
necessary to be analysed and researched before implementing the design and infrastructure of
a network.
Application and Analysis
 Model for network designing
A widely adopted network model for designing a highly scalable and reliable network
infrastructure is a three-layer hierarchical networking model. A network design always
varies according to the size and necessities of the organizations. The requirements definitely
decide the complexity of the network. Hierarchical network design consists of 3 functional
layers. Earlier, a flat topology was used to deploy networks. But with advancement in
technology, number of devices and applications increased and switches and hubs were added
to connect more devices which resultantly degraded response time and made the network
unusable. Due to this reason, the hierarchical model was adopted.

Fig: Hierarchical Network
This model divides the entire network into three discrete layers namely, access layer,
distribution layer and core layer. Each of these layers have their own specific functionalities.
A flat topology is moved to such manageable and modular model to let the local traffic
remain local and pass only the one that is destined to outer networks.
Two-tier collapsed core design is a hierarchical design in which two layers i.e. distribution
layer and core layer are collapsed into a single layer and their functionalities are performed
by a single device. This gives rise to a collapsed core and increases the network performance
and availability and its ability to get scalable according to the requirement. It maintains most
of the functionalities and benefits of the three-tier model making it more cost efficient.

Fig- Two-tier hierarchical network model design
 Network Components used
To design the network infrastructure according to the scenario given, we will be using four
layer-2 switches of model 2960TT-24TT to create four VLANs for four separate departments
as given in the scenario which are resultantly connected to a single multilayer switch in the
collapsed core layer. Here, we have used a 3560-24PS model layer 3 switch for better
network routing performance for interconnectivity between the virtual LANs of the large
corporate network. These switches have lesser network latency while making routing
decisions. They are used to enhance routing capabilities between virtual LANs by reducing
the amount of broadcast traffic, simplify security management and improve fault isolation.
Thus, layer 3 switches are preferable for distribution layer.
As, we need to make the network scalable, so we wireless switch so as to use as many ports
in future as required and have a wireless connection. The multilayer switch used in the
collapsed core layer can act as a router anytime according to our requirement. The other layer
2 switches in the access layer have a number of interconnected PCs and printers indicating 4
separate departments as mentioned in the scenario.
A layer 3 switch of model 3560 24PS is used and configured as trunk to host 4 servers
namely, web server, file server, email server and DNS server, which will be accessible to the
users of all the four departments. This switch has the ability to act as a router as and when
required. Also, a router is used for future connections to other networks.

Evaluation of Different Technologies Used
 VLANs: VLAN also termed as Virtual LAN is a technology which divides the devices on
data link layer logically. VLAN divides the broadcast domain by switches. VLAN is a
concept which allows a network manager to divide a LAN logically into different
segments or broadcast domains. It definitely does not imply a physical segmentation but a
logical one. It is a partitioned broadcast isolated in a network of computers at layer 2 of
OSI model.
 Trunking: Trunking is done to provide connection between switching centres in a
network. It is link which is designed with the intention to carry various signals all at the
same time so as to provide proper network access between the two points. Computer
networks incorporated 2 types of trunk modes: firstly, the one in which trunk port is used
as a single interconnection medium on switches or routers to carry data from various
LANs or VLANs; secondly, port trunking is done so as to bond various physical links in
order to create a single logical link which is more reliable and of a higher capacity.
 Network Access Control: Network Access Control is a concept adopted to meet
endpoint security. It is a solution in computer networks which makes use of a set of
protocols to define policies that would describe how securely the network nodes can be
accessed by any device when there is an attempt made to access the network. NAC is a
network security management that enforces security policies and compliances of access
control for a network. It tends to be a security solution that allows only trusted and
authorised endpoint devices to access the entire infrastructure and resources of the
network.
 DHCP: DHCP is Dynamic Host Configuration Protocol that enables a server to assign IP
addresses to devices within the configured scope of a given network automatically. It uses
DHCPDISCOVER, DHCPOFFER, DHCPREQUEST and DHCPACK packets for entire
IP assignment process.
 VTP: VLAN Trunk Protocol abbreviated as VTP is a protocol that carries the VLAN
information on the entire LAN i.e. to all switches in the entire VTP domain.

Design, Implementation and Testing
As already discussed about the networking components and the protocols and technologies
used for implementing the given scenario, let us now have a look at the resultant network
diagram and the configurations done for successful implementation of case study:
Network Design
Below shown is the network diagram which has four layer 2 switches indicating 4
departments of a company connected to a single multilayer switch for better network routing
performance. These layer 2 switches have PCs and printers connected; and the two
departments which had more number of required PCs such as 68 and 48 have a wireless
switch attached to them so as to use the number of ports as required and have a portable
wireless connection. Another layer 2 switch is used and configured with a trunk port to host
the four servers and make them accessible to the entire department. A router is used at the
topmost layer so as to have future connections with outer networks and for ACL
configuration the router is mandatory to deny the traffic of VLANs.
Fig: Illustration of the network design
VLAN Configuration
As provided in the scenario, there are 4 different departments in the company and this could
be formed by configuring 4 VLANs. By default, all the devices connected to a switch fall
under VLAN 1. Four separate departments are formed by configuring VLANs for them on
the multilayer switch. VLAN configuration is shown below:

Figure 1: VLAN creation and configuration

Figure 2: Showing the created VLANs for all 4 departments
VTP Configuration
Below given figure represents the configuration of the multilayer switch as a VTP server so
as to carry the VLAN information within the entire VTP domain:
Figure 3: Showing the VTP configuration
Trunk Port configuration
The multilayer switch is configured with a trunk port so as to have a successful inter VLAN
connection. Each department is assigned a layer 2 switch and is configured with a separate
VLAN, thus trunk port configuration is done on the multilayer switch with the intention to

provide proper network connection between the switching centres within the network. Below
shown is the configuration of trunk port on the multilayer switch:
Figure 4: Trunk port configuration
Now, below shown figure shows the trunk mode configuration of giga ethernet interface of
every layer 2 switch so as to provide permission to carry traffic from multiple VLANs all at
the same time: