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Chapter 2 - Network Design

Uditha Atukorala's picture

To facilitate 220 terminals and wireless users in a building eight switches are used. All of these switches provide Fast Ethernet (100Mbps) ports with additional Gigabit Ethernet (1000Mbps) uplink ports giving 100Mbps access layer with a 1000Mbps backbone.

As shown in Figure 2-1 these switches are cascaded if needed and connected to a router (RT_DIST).

 

Backbone Network 
Figure 2-1

 

The router (RT_DIST) performs routing and controls traffic for logical LAN segments and for the internet link.

All the servers are connected to the switch SW_SVR. This switch is then connected to the router RT_DIST with its 1000Mbps uplink. Figure 2-2 shows the network design for the server farm. Switch SW_SVR is also connected to the access point WBR, mounted on top of the building with Cisco 13.5 dBi Yagi antenna, which is configured as a bridge to connect the two server segments of LANs in the two buildings.

The servers are allocated the IP addresses from the subnet 10.0.0.0/8. For easy administration, servers in building A is allocated IP addresses from 10.0.1.1/8 to 10.0.1.252/8 and building B is allocated IP addresses from 10.0.2.1/8 10.0.2.252/8. The WBR bridging access points are allocated 10.0.1.253/8 and 10.0.2.253/8 IP addresses. 

 

Server Farm

Figure 2-2

 

All the 20 ground floor terminals are connected to the switch SW_GND and that switch is connected to the switch SW_EMP located in fourth floor, which is connected to the wireless access points giving access to only the company employees. This connectivity is shown Figure 2-1 and Figure 2-3 exhibits the ground floor network design.

Switch SW_GND is connected to a DHCP server which assigns IP addresses for employees (including wireless clients) from the subnet 192.168.1.0/24 for building A and from the subnet 192.168.11.0/24 for building B.

Second and third floors are having the same network designs which are shown in Figure 2-4 and Figure 2-5. On second floor the terminals are connected to SW_2ND1 and SW_2ND2 which are connected together with 1000Mbps uplinks. SW_2ND1 is connected to a DHCP server which assigns IP addresses to terminals in classrooms on second and third floors from the subnet 192.168.2.0/24 for building A and 192.168.12.0/24 for building B.

All the terminals on third floor classrooms are connected to switches SW_3RD1 and SW_3RD2 which are connected together with 1000Mbps uplinks. Additionally the SW_3RD1 is connected to SW_2ND2 with a 1000Mbps uplink port.

 

Ground Floor

Figure 2-3

 

2nd Floor

Figure 2-4

 

3rd Floor

Figure 2-5

 

The 40 terminals giving access to guests on fourth and fifth floors are connected to the switch SW_OPEN_48. A DHCP server connected to SW_OPEN_48 assigns IP addresses for all the 40 guest terminals and wireless guests from the subnet 192.168.4.0/24 for building A and 192.168.14.0/24 for building B.

In order to give wireless access to both guests and employees there are 3 wireless access points configured for guest access and 3 access points configured with WEP security for employee access in the fourth floor. And in fifth floor there are 4 access points giving guest access and 4 access points configured for employee access with WEP security.

In fourth floor, except for two all the other access points are mounted on the ceiling with Cisco 2.2 dBi ceiling mount diversity patch antennas. Two access points are mounted on the West side wall with Cisco 8.5 dBi patch antennas.

Access points on fifth floor are mounted on the four walls with Cisco 8.5 dBi patch antennas on East and West side walls and Cisco 6 dBi diversity patch antennas on North and South walls.

Figure 2-6 shows the network design for fourth floor and Figure 2-7 shown the network design for fifth floor. Figure 2-8 and Figure 2-9 exhibits wireless coverage for fourth and fifth floors respectively.

 

4th Floor

Figure 2-6

 

5th Floor

Figure 2-7

 

4th Floor - Access Point Coverage

Figure 2-8

 

5th Floor - Access Point Coverage

Figure 2-9

 

All the access points on both fourth and fifth floors are configures to operate in 802.11a and 802.11g standards with all the data rates below 11Mbps blocked.

As shown in Figure 2-8, wireless coverage is accomplished by three non-overlapping channels in fourth floor. And in fifth floor (Figure 2-9), North and South wall mounted access points operate in the same channel and East and West wall mounted access points operate in another two non-overlapping channels.

All the access points are powered through the Ethernet cables.