【Wireshark Lab v8.0】Lab8：DHCP

ipconfig/release

ipconfig/renew

1. Are DHCP messages sent over UDP or TCP?

   UDP

2. Draw a timing datagram illustrating the sequence of the first four-packet Discover/Offer/Request/ACK DHCP exchange between the client and server. For each packet, indicated the source and destination port numbers. Are the port numbers the same as in the example given in this lab assignment?

   时序图待补充

   Discover：src 68 dst67

   Offer：67 68

   Request：68 67

   ACK DHCP：67 68

   相同

3. What is the link-layer (e.g., Ethernet) address of your host?

   

4. What values in the DHCP discover message differentiate this message from the DHCP request message? （待补充）

   

   

5. What is the value of the Transaction-ID in each of the first four (Discover/Offer/Request/ACK) DHCP messages? What are the values of the Transaction-ID in the second set (Request/ACK) set of DHCP messages? What is the purpose of the Transaction-ID field?

   0x3e5e0ces

   0x257e55a3

   区分不同次的dhcp服务

6. A host uses DHCP to obtain an IP address, among other things. But a host’s IP address is not confirmed until the end of the four-message exchange! If the IP address is not set until the end of the four-message exchange, then what values are used in the IP datagrams in the four-message exchange?（待补充） For each of the four DHCP messages (Discover/Offer/Request/ACK DHCP), indicate the source and destination IP addresses that are carried in the encapsulating IP datagram.

   

7. What is the IP address of your DHCP server?

   255.255.255.255

8. What IP address is the DHCP server offering to your host in the DHCP Offer message? Indicate which DHCP message contains the offered DHCP address.

9. In the example screenshot in this assignment, there is no relay agent between the host and the DHCP server. What values in the trace indicate the absence of a relay agent? Is there a relay agent in your experiment? If so what is the IP address of the agent?

10. Explain the purpose of the router and subnet mask lines in the DHCP offer message.

11. In the DHCP trace file noted in footnote 2, the DHCP server offers a specific IP address to the client (see also question 8. above). In the client’s response to the 3 What do we mean by “annotate”? If you hand in a paper copy, please highlight where in the printout you’ve found the answer and add some text (preferably with a colored pen) noting what you found in what you ‘ve highlight. If you hand in an electronic copy, it would be great if you could also highlight and annotate. first server OFFER message, does the client accept this IP address? Where in the client’s RESPONSE is the client’s requested address?

12. Explain the purpose of the lease time. How long is the lease time in your experiment?

13. What is the purpose of the DHCP release message? Does the DHCP server issue an acknowledgment of receipt of the client’s DHCP request? What would happen if the client’s DHCP release message is lost?

14. Clear the bootp filter from your Wireshark window. Were any ARP packets sent or received during the DHCP packet-exchange period? If so, explain the purpose of those ARP packets