An Ethernet Packet Analysis With Wireshark Computer Science Essay

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This lab is particularly required the student to connect multiple network and liked them together as they can access to each other. From the previous lab, it had been clearly stated how to connect two network by using crossover cable. In the further question, it is require us to connect three networks by using 2 crossover cables by using an addition NIC in one of the PC 1. There are few command we use during lab session for example ping <IP address> is use to ping the other PC in the network connected, route print is used to output the routing table, route <ADD> <network IP address> <mask> <default gateway> IF <network interface number> is used to add new route into the routing table.

ADDITIONAL QUESTION:

Please suggest how you would link all the three networks together by replacing the 4-port switch (192.168.d.0) with another network interface card (the network interface card can be installed into any of the PC). You are required to provide the following details in your solution.

The drawing of your network configuration. Please clearly state all the network number and the IP address for each of the network interface card.

The configuration of the routing table.

The reason you have chosen the configuration.

ANSWER:

lab2.jpg

TABLE 1: IP address of each of the NIC in the PC 1 in each network

Network interface card (NIC)

IP Address

PC 1 (NIC 1, network 3)

192.168.3.2

PC 1 (NIC 2, network 3)

192.168.0.3

PC 1 (NIC 3, network 3)

192.168.0.4

PC 1 (NIC 1, network 6)

192.168.6.2

PC 1 (NIC 2, network 6)

192.168.0.6

PC 1 (NIC 1, network 9)

192.168.9.2

PC 1 (NIC 2, network 9)

192.168.0.9

The PC1 (NIC 1) for each network have the same last bit of the IP address. This is due to each of the server (switch) in each network act as the first address. The only thing different between each of the IP address is from the network number, which is the second last bit. It is either 3 (network 9), 6 (network 9) or 9 (network 9).

The second last bit of the IP address of the second NIC is set to 0 so that all the PC 1 second NIC is referred to the same network which linked them together. The number (0) can be other 0 as long as it is not 3, 6 or 9 to avoid the crashing of IP address of the PCs.

The command use to insert the new route line is:

Route add 192.168.6.0 mask 255.255.255.0 192.168.0.3 IF <network interface (IFi) number>

Route add 192.168.9.0 mask 255.255.255.0 192.168.0.4 IF <network interface (IFi) number>

TABLE 2: TCP/IP properties for the LAN network contains three network

IP Address

Subnet Mask

Default Gateway

Switch (number 3)

192.168.3.1

-

-

PC 1 server 1 st card

192.168.3.2

255.255.255.0

-

PC 2

192.168.3.3

255.255.255.0

192.168.3.2

PC 3

192.168.3.4

255.255.255.0

192.168.3.2

Switch (number 6)

192.168.6.1

-

-

PC 1 server 1 st card

192.168.6.2

255.255.255.0

-

PC 2

192.168.6.3

255.255.255.0

192.168.6.2

PC 3

192.168.6.4

255.255.255.0

192.168.6.2

Switch (number 9)

192.168.9.1

-

-

PC 1 server 1 st card

192.168.9.2

255.255.255.0

-

PC 2

192.168.9.3

255.255.255.0

192.168.9.2

PC 3

192.168.9.4

255.255.255.0

192.168.9.2

TABLE 3: TCP/ IP properties for 2nd network card in LAN contains two network (network 3 and 6)

IP Address

Subnet Mask

Default Gateway

PC 1 (server, network 3)

192.168.0.3

255.255.255.0

192.168.0.6

PC 1 (server, network 6)

192.168.0.6

255.255.255.0

192.168.0.3

TABLE 4: TCP/ IP properties for 2nd network card for PC 1 in network 3 and 3rd network card for PC 1 in network 1 in LAN contains two network (network 3 and 9)

IP Address

Subnet Mask

Default Gateway

PC 1 (server, network 3)

192.168.0.4

255.255.255.0

192.168.0.9

PC 1 (server, network 9)

192.168.0.9

255.255.255.0

192.168.0.4

For the third network, the IP address used is 192.168.3.n, where n is stand for number of PC used start from 2 because the switch served as number 1.

For the sixth network, the IP address used is 192.168.6.n, where n is stand for number of PC used start from 2 because the switch served as number 1.

For the ninth network, the IP address used is 192.168.9.n, where n is stand for number of PC used start from 2 because the switch served as number 1.

It is important that a switch did not serve a subnet mask (255.255.255.0).

The default gateway is showing where the particular PC should refer to. And this is normally set to the PC 1 which have more than 1 NIC.

To set up the crossover line IP address between two PC 1, the IP address is referring to the address of itself and default gateway is set to the other PC 1 which is connected together as we can see in table 3 and table 4.

It should be noted that each of the PC in a same network should not use the same IP address to avoid the IP conflict problem. The range can be set from 192.168.n.2 to 192.168.n.254 where n is stand for network number.

For the subnet mask, it had been set to 255.255.255.0 for masking the IP address and divides the IP address into two addresses which is host address and network address. In binary format, the subnet mask becomes 11111111.11111111.11111111.00000000. The 1 is stand for the network bits and 0 is for the host bits. The 0 is assigned to a network address and 255 is assigned to a broadcast address.

The default gateway act as the LAN between each of the network or allowing them to connect to the internet. Therefore, the first PC of the network is no need to be set and the rest of the PC is set to the same as the IP address of PC 1.

As mentioned early, the network bit (second last nit) of the NIC is set to 0 for referring them to the same network. As we can see in Table 3 and 4, the entire network bit is set to 0. The default gateway of the entire NIC is set to the IP address of the PC 1 which is linked to it. In other words, it has the opponent IP address for its default gateway.

As a brief explanation, this connection is created by using the idea of a point-to-point topology as the backbone and bus topology among each of the PCs in a particular network connection. To connect a PC as a server to another PC, point-to-point topology is selected although it is not the best way to link two or more networks together. Besides, by using this method to connect the two networks together, it is a straight forward method by using a crossover cable, the transmit time is slightly faster theoretically due to the lesser cable have to pass over. Furthermore, due to the lesser cable had been used, the cost to do extra cable can be avoided and so is the extra one 4-port switch. By using this type of connection, the path to pass through from 1 PC to another PC is other network is lesser. For example, PC 3 in network 3 needs to connect to PC 3 in network 9. The path pass through is 5 path. By comparing using to the connection using switch, 6 path is required to pass though.

In between, there is a few disadvantage of using this kind of connection. Firstly, the connection for numbers of network is limited. This is due to the limited NIC can be installed in a PC. And even it can be installed in a PC, the cost required to buy a motherboard that can support few NIC is high. Therefore, it is better to use a switch to link few network together. In the nutshell, it is very tedious to set up a connection between networks by using this method. Various IP address is needed for each PC and more IP address in the PC that installed extra NIC. Besides, when connecting the network together, it is a must to differentiate a crossover cable and a strip cable. If a crossover cable is use to connect within a network PC it will failed to ping other PC in a network. Same goes to the connection within PC 1 and PC 1 in different network. If a strip cable is use for that particular connection, it would not be able to ping each other.

CONCLUSION:

Throughout this lab session, each of the IP address, net mask and default gateway of every PCs in a LAN network is clearly understood. Each of the function had been clearly stated in the report and set during the lab session. If the IP address, net mask or default gateway had been set wrongly, the PC would not be able to ping another PC from another network or even in its own network. More importantly, the destination of the packet could not be reach while the source packet could not be sent. Besides, the routing table for the overall network also had been predicted for the question 8. While for the question 7, the routing table is configured using ‘route print’ command in RUN program. Furthermore, in the question 8, it is required to link 3 network together instead of using the forth switch but by using additional NIC in one of the PC 1. For this particular question, I had installed the extra NIC in the PC 1 in the network 3 and linked the second and third NIC to network 6 and network 9. Files or folder for sharing purpose had been shown working during the lab session by changing the content of the file. But before the file can be access by another PC, all the setting should be ensured correct or else error will occur. Right before the end, the WireShark program had been used to capture the ICMP packet generated by the ping program. This can be done when pinging the other user/ PC by using the RUN program and WireShark will show the source and destination address.

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