通信网原理实验报告Ethernet and ARP(2)

my subnet.

7. What is the destination address in the Ethernet frame? Is this the Ethernet address of your computer? Answer：

1)The destination address in the Ethernet frame is:c8:0a:a9:db:9b:f3 2)It is the address of my computer.

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

8. 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: 0x0800.

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

Flag field

9. How many bytes from the very start of the Ethernet frame does the ASCII “O” in “OK” (i.e., the HTTP response code) appear in the Ethernet frame? Answer：

1)The ASCII “O” 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.

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

1)There is no CRC field.

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

(二)The Address Resolution Protocol （1）ARP Caching

11. Write down the contents of your computer’s ARP cache. What is the meaning of each column value?

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Answer：

1)The Internet Address column contains the IP address,.

2)The Physical Address column contains the MAC address, and the type indicates the protocol type. 3)Observing ARP in action

12. What are the hexadecimal values for the source and destination addresses in the Ethernet frame containing the ARP request message? Answer：

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1)The hexadecimal values for the source addresses in the Ethernet frame containing the ARP request message is: 00:23:89:8d:50:71

2)The destination addresses in the Ethernet frame containing the ARP request message is: ff:ff:ff:ff:ff:ff

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

The hexadecimal value for the two-byte Ethernet Frame type field is:0x0806.

14. Download the ARP specification from

ftp://ftp.rfc-editor.org/innotes/std/std37.txt. A readable, detailed discussion of ARP is also at

http://www.erg.abdn.ac.uk/users/gorry/course/inet-pages/arp.html. a) How many bytes from the very beginning of the Ethernet frame does

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the ARP opcode field begin?

Answer：The ARP opcode field begins 20 bytes from the very beginning of the Ethernet frame.

b) What is the value of the opcode field within the ARP-payload part of the Ethernet frame in which an ARP request is made?

Answer：The hex value for opcode field withing the ARP-payload of the request is 1.

c) Does the ARP message contain the IP address of the sender?

Answer：Yes, the ARP message containg the IP address 192.168.1.105 for the sender.

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