A router is a networking device whose software and hardware are designed to perform the task of routing and forwarding information. Routers connect two or more subnets. Linksys 54G2 is a router used to share Internet connections with several computers via 802.3 Ethernet and 802.11b/g wireless connection. It has four Ethernet ports and one WAN port as shown in the Figure below.
The Internet port is where connection to wide area network is made. The Ethernet ports connects the router to the PCs in the local area network or other network devices. The reset button restores the router to its default settings. In order to perform reset, the reset button should be pressed for at least 5 seconds. The power port needs to be connected to the power adapter. The front panel consist of some LED indicators and a push button as shown below.
The four Ethernet LEDs corresponds to the four ports at the back panel. They serve two purposes. If continuously lit, it means the routers is connected to a device through the port indicated. A blinking LED means there is network activity at the particular port. The WIFI protected Setup (WPS) button automatically sets up wireless security for the wireless network. If the LED is green, wireless security is enabled. It turns amber when an error is present. The wireless LED lights up when the wireless feature is enabled. It flashes when there is a network activity. The power LED flashes when the router is undergoing self-diagnostic mode during every start up. When done it is solid lit.
Wireshark
The basic tool to observe the messages exchanged between protocols is known as a packet sniffer. It has the ability to capture messages being transmitted from/by computer; it also stores and displays content in captured messages. A packet sniffer is passive. It observes and records but never sends packets itself. Similarly, received packets are never explicitly addressed to the packet sniffer. Instead, it receives a copy of packets that are sent/receive from/by application and protocols executing on the computer.
The figure above shows the structure of packet sniffer. On the right are protocols and applications. The packet capture library receives a copy of every link layer frame sent/received by the computer.
The second component of the packet sniffer is the packet analyzer which displays the contents of all the fields within a protocol message. The packet analyzer understands the structure of all messages exchanged by protocol. It also understands the IP datagram format, so it can extract the TCP segment within the IP datagram. It also extracts HTTP messages. Finally, it understands the HTTP protocol as such it knows the first bytes of an HTTP message will contain "GET","POST" or "HEAD".
The Wireshark interface has 5 major components:
-Command menus-pull down menu
-Packet listing window-display one line summary
-Packet header details window-provides details about packet selected
-Packet contents window-displays entire content of captured frame
-Packet display filter field- protocol name or other information can be entered in order to filter information.
Discussion
C.1 Experiment 1
C.1.2 Setting up the router
Router X
MAC address: 00:21:29:89:57:6A
IP address: 10.102.73.110
C.1.3 Analyzing the Network
Computer A
Physical address: 00:16:76:CA:EB:4E
IP address: 192.168.1.101
Subnet mask: 255.255.255.0
Default gateway: 192.168.1.1
Computer B
Physical Address: 00:16:76:CA:EE:31
IP address: 192.168.1.100
Subnet mask: 255.255.255.0
Default gateway: 192.168.1.1
Can both computer A & B connect to the Internet?
Yes, both can be connected to the internet
How many Ping request and Ping reply packets have been captured?
4 ping request and 4 ping reply
Indicate whether the source and destination MAC addresses and IP addresses of the Ping Request Packets are the same as the MAC address and IP address of computer A, computer B or router X? Explain your observation
Yes they are the same. Since,
Indicate whether the source and destination MAC addresses and IP addresses of the Ping Reply Packets are the same as the MAC address and IP address of computer A, computer B or router X? Explain your observation
Yes they are the same. Since,
Can computer B receive the Ping request from computer A? Explain your observation.
Yes, computer B can receive the Ping request from computer A because
C.2 Experiment 2
C.2.1 Setting up the Network
C.2.2 Setting up the Router
Router Y
MAC address: 00:21:29:9D:E7:43
Router X
MAC address: 00:21:29:89:57:6A
IP address: 10.102.73.110
C.2.3 Analyzing the Network
Computer A
Physical address: 00:16:76:CA:EB:4E
IP address:192.168.1.101
Subnet mask: 255.255.255.0
Default gateway:192.168.1.1
Computer B
Physical address: 00:16:76:CA:EE:31
IP address:192.168.1.100
Subnet mask: 255.255.255.0
Default gateway:192.168.1.1
Note down the source and destination MAC address and IP address of all request and reply packets
Indicate whether the source and destination MAC addresses and IP addresses of the Ping Request Packets are the same as the MAC address and IP address of computer A, computer B, router X or router Y? Explain your observation
Indicate whether the source and destination MAC addresses and IP addresses of the Ping Reply Packets are the same as the MAC address and IP address of computer A, computer B, router X or router Y? Explain your observation
Can computer B receive the Ping request from computer A? Explain your observation?
What is the role of router Y in this network configuration?
C.3 Experiment 3
C.3.1 Setting up the Network
C.3.2 Setting up Router
Router Y
MAC address: 00:21:29:9D:E7:43
IP address: 192.168.1.100
Router X
MAC address:00:21:29:89:57:6A
IP address:10.102.73.110
C.3.3 Analyzing the Network
Computer A
Physical address:00:16:76:CA:EB:4E
IP address:192.168.1.100
Subnet mask:255.255.255.0
Default gateway:192.168.1.1
Computer B
Physical address:00:16:76:CA:EE:31
IP address:192.168.2.100
Subnet mask:255.255.255.0
Default gateway:192.168.2.1
Can both computer A and B connect to the Internet?
Yes, they both can connect to the internet.
Note down the source and destination MAC addresses and IP addresses of all request and reply packets
Indicate whether the source and destination MAC addresses and IP addresses of the Ping Request Packets are the same as the MAC address and IP address of computer A, computer B, router X or router Y? Explain your observation
Indicate whether the source and destination MAC addresses and IP addresses of the Ping Reply Packets are the same as the MAC address and IP address of computer A, computer B, router X or router Y? Explain your observation
Can computer B receive the Ping request from computer A? Explain your observation.
Conclusion
