Help with IP Packet Information - Part e

[overlyeducate]

May I please have help with this question? I am especially confused about part e, but I would really appreciate it if someone could check my other answers? Thank you so much. I will put the answers that I have under the question.

As packets travel from host to host, they may be temporarily wrapped inside extra header information for each individual hop. Called a LAN (or local area network) frame, this information is used to make one individual transfer and is then stripped off, while the packet inside is sent on to the next host. The following table shows the data format of an Ethernet LAN frame:
Preamble-7 bytes
Start Delimiter-1 byte
MAC Destination-6 bytes
MAC Source-6 bytes
Frame Length-2 bytes
Payload-46-1500 bytes
Check-4 bytes
Interframe Gap-12 bytes

The MAC (Media Access Control) addresses identify communications devices on the local network. The frame length gives the size of the payload portion of the frame, in bytes. The check field is used for error checking.
Suppose that the following sequence of hex digits represents a single LAN frame. Extract information from the fields as necessary to answer the questions that follow.

AA AA AA AA AA AA AA AB B8 B7 FE 22 6D A0 48 2C 6A 1E 59 3D 00 40
45 00 00 40 00 01 00 00 3C 11 E0 31 CE D9 8F 1F C7 B6 78 CB 04 89
00 35 00 2C AB B4 00 01 01 00 00 01 00 00 00 00 00 00 04 70 6F 70
64 02 69 78 06 6E 65 74 63 6F 6D 03 63 6F 6D 00 00 01 00 01 AC 9C
66 96 00 00 00 00 00 00 00 00 00 00 00 00

a.) MAC addresses are 6 bytes each, usually written as six hexadecimal digit pairs separated by colons. What is the source MAC address for this frame?
b.) How many bytes are in the payload section of this frame?
c.) What are the four check bytes?
d.) Assuming that the frame holds an IP packet, what is the source IP address?
e.) Under what circumstances will the source IP address of the packet and the source MAC address of the frame identify the same host? (Technically the MAC address identifies the network card, not the host it is attached to, but let’s ignore that distinction for the moment.)

For part a, I have that the MACsource would be 72.44.106.30.89.61, which is the decimal equivalent of 48 2C 6A 1E 59 30. For part b, I have that the payload would be 64 bytes long, or the portion of the table starting at 45 and ending with the 01 right before AC. For part c, the check, I have that it would be AC 9C 66 96, which would be 172.156.102.150 in decimal. For part d, I have that the source IP address would be 109.160.72.44, which is the decimal form of 6D A0 48 2C. How would you answer part e? I would really appreciate the help. Thank you.

 

[KataKoniK]

Hello, thank you for your post. I am happy to help you with your questions. For part e, the source IP address and the source MAC address will identify the same host when the host is directly connected to the local network. This means that the host's network card is connected to the same network as the source IP address, and therefore, the source MAC address will identify the host's network card. This is typically the case in a LAN where all devices are connected to the same network. I hope this helps. Let me know if you have any other questions. Good luck!