通信网原理实验报告Ethernet and ARP

实验一 Ethernet and ARP

一、实验目的

1.加强对以太网帧格式的理解； 2.理解ARP协议的工作原理。 二、实验环境 1.PC机一台； 2.WireShark软件。 三、实验内容

1. Capturing and analyzing Ethernet frames 2. The Address Resolution Protocol 四、实验步骤及思考

（一）Capturing and analyzing Ethernet frames

HTTP GET Message

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(1)Based on the contents of the Ethernet frame containing the HTTP

GET message

1. What is the 48-bit Ethernet address of your computer?

Answer：The 48-bit Ethernet address of my computer is:c8:0a:a9:db:9b:f3

The Ethernet address of my computer

2. What is the 48-bit destination address in the Ethernet frame? Is this the Ethernet address of gaia.cs.umass.edu? (Hint: the answer is no). What device has this as its Ethernet address?

[Note: this is an important question, and one that students sometimes get wrong. Re-read pages 468-469 in the text and make sure you understand the answer here.]

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Answer：

1)The 48-bit destination address in the Ethernet frame is:00:23:89:8d:50:71

The destination address in the Ethernet frame

2)This is not the Ethernet address of gaia.cs.umass.edu.

3)It is the address of my Linksys router, whick is the link used to get off the subnet.

3.Give the hexadecimal value for the two-byte Frame type field. What do the bit(s) whose value is 1 mean within the flag field? Answer：

1)The hexadecimal value for the two-byte Frame type field is:ox0800

The hexadecimal value for the two-byte Frame type

2) The value is 1 within the flag field means the fragment has not been fragmented.

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Flag

4.How many bytes from the very start of the Ethernet frame does the ASCII “G” in “GET” appear in the Ethernet frame? Answer：

1)The ASCII “G” appears 54 bytes from the very start of the Ethernet frame. 2)Calculation process as follows:There are 14 bytes of Ethernet frame,20 bytes of IP header and 20 bytes of TCP header before HTTP data is encountered.

5. What is the hexadecimal value of the CRC field in this Ethernet frame? Answer：

1)There is no CRC field.

2)Because the CRC calculated before the Wireshark packet sniffer start up.

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(2)Based on the contents of the Ethernet frame containing the first byte of the HTTP response message

6. What is the value of the Ethernet source address? Is this the address of your computer, or of gaia.cs.umass.edu (Hint: the answer is no). What device has this as its Ethernet address? Answer：

1)The value of the Ethernet source address is: 00:23:89:8d:50:71

HTTP response message

2)This is neither the address of your computer,northe address of gaia.cs.umass.edu.

3)It is the address of my Linksys router,which is the link used to get onto

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