HOMEWORK ASSIGNMENT

Week 1

30 Points Maximum

Name ______Tommy Delatorre________________________________

NETW204

Homework #1

Due Date ____________________11/20/19_________________

Professor ________________Winston Park ______________________ 

Switching Concepts

1. Look at the Ethernet header below. Explain the following fields in the Ethernet header.

(10 points, 2 points for each correct field explained.)

a. Preamble:

b. Destination Address:

c. Length: This field is 2 bytes i.e., 16 bits, this indicates the length of entire Ethernet Frame. Even though, the value of this field can range from 0 to 65534, its length cannot be larger than 1500 as Ethernet has some hardware limitations.

d. Data: This is also known as Payload. This is the field where we insert the actual data. When Internet Protocol is used over Ethernet, both IP header and actual data will also be inserted in this field. The maximum data that can be represented using this field can range from 46 to 1500 Bytes. if the data length is less than 46 bytes, then padding 0’s will be added to meet the minimum possible length requirement.

e. FCS: This stands for Frame Checksum. It is of 4 bytes. This field is used as error detection code. This is used to detect any error present in the payload.

2. You are the most recently hired network engineer out of a group of 10 network engineers. During a meeting to implement a new switching technology, your manager asks the team to decide on which switching forwarding technique to use—cut-through or store-and-forward. You are required to come up with advantages and disadvantages of using both cut-through and store-and-forward. What would your list entail? Provide support for each item in your list. (10 points)

Store and forward are the suggested names that the switch receives a frame on a port and stores the frame in its memory buffer until the frame has been completely received. The switch analyzes the frame for information about its destination and uses CRC. After confirming its integrity, the frame is forward out the correct port and toward its destination. If a frame is corrupted the switch discards it and less bandwidth is wasted on the unusable frame.

Some of the advantages could be, is the improved integrity of the data transmitted across these switches.

Some of disadvantages could be A These switches are used mainly in networks with poor connectivity or poor transmission capabilities and the need for fewer errors outweigh the need for real time communications.

The Cut-through switching acts on the data as soon as it is received, even if the transmission is not complete! The switch only buffers enough of the frame to read the destination MAC address so that it can then decide where to send the frame. This is in the first 6 bytes of the frame. The switch looks at the MAC address in its own MAC address table and starts to forward the frame. The switch does not perform any error checking on the frame because it can start forwarding the frame immediately after the first 6 bytes.

3. Explain how each of the following commands below will impact the switched network? Which command is the default command used when setting up port-security on a Cisco switch? (10 points)

a. switchport port-security violation protect

b. switchport port-security violation shutdown

c. switchport port-security violation restrict

Switchport port-security violation protect: This command silently drops traffic that is in violation until the number of secure addresses drop below the maximum value.

Switchport port-security violation shutdown: This command immediately puts the port into the “errordisabled” state, drops all traffic, and sends a SNMP trap notification.

Switchport port-security violation restrict: This command behaves like protect but also increments the security violation counter for each violation and sends a SNMP trap notification.

The default command used when setting up port-security on a cisco switch is Switchport port-security violation shutdown.

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