HELP WITH ARP REQUEST
bearfan
Member Posts: 70 ■■□□□□□□□□
in CCNA & CCENT
Is this a forum where you can post CCNA questions you have trouble understanding? If not, let me know.
This is a Transcenders practice test question I simply can't get correct.
In this scenario, you are downloading a file from the TFTP Server to the PC. What addresses
are present in the frames on the local network when the data returns from the TFTP Server?
(choose four).
There is a picture of 2 network separated by Router A, the Internet and Router B. The TFTP Server is on one network and the PC on the other.
A. IP address of the PC
B. MAC address of the PC
C. IP address of the TFTP Server
D. MAC address of the TFTP Server
E. IP and MAC address of the local routers ethernet port
F. IP and MAC address of the remote routers serial port
G. MAC address of both switch ports
I guess I don't fully understand exactly what information is in the ARP request at what point.
Can anyone shed some light?
Note: In this example the correct answers are A,B,C, and E. But I want to understand why. Also, there are other similar practice questions and it seems the answer to what's in the packet or frame can vary depending on where its at.
This is a Transcenders practice test question I simply can't get correct.
In this scenario, you are downloading a file from the TFTP Server to the PC. What addresses
are present in the frames on the local network when the data returns from the TFTP Server?
(choose four).
There is a picture of 2 network separated by Router A, the Internet and Router B. The TFTP Server is on one network and the PC on the other.
A. IP address of the PC
B. MAC address of the PC
C. IP address of the TFTP Server
D. MAC address of the TFTP Server
E. IP and MAC address of the local routers ethernet port
F. IP and MAC address of the remote routers serial port
G. MAC address of both switch ports
I guess I don't fully understand exactly what information is in the ARP request at what point.
Can anyone shed some light?
Note: In this example the correct answers are A,B,C, and E. But I want to understand why. Also, there are other similar practice questions and it seems the answer to what's in the packet or frame can vary depending on where its at.
Comments
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Webmaster Admin Posts: 10,292 Adminbearfan wrote:Is this a forum where you can post CCNA questions you have trouble understanding? If not, let me know.
Anyway, no biggie. And to answer your question, it's not directly ARP related. The PC is already downloading frames from the TFTP server, so the ARP process took place already.
In general, with IP communication across networks the destination address will be the MAC + IP address of the PC and the source IP address will be the IP address of the original sender (i.e. the TFTP server) and the source MAC address will be the router's interface closest to the PC (which is typically the default gateway). So IP addresses stay the same when a packet cross networks (/routers, unless NAT is used), but the MAC address in the frame that hold the packet will change. -
Pash Member Posts: 1,600 ■■■■■□□□□□Just to add to Johan's post:
On that local router interface to the PC, if it isnt already in ARP cache the router will ARP broadcast to obtain the correct L2 destination.
Effectively it's exactly like:
OI! Whos got 192.168.1.50??? FF:FF:FF:FF:FF:FF (example)
Then the PC replies with an ARP reply, a unicast to the router interface who asked for the L2 address of 192.168.1.50.
I suggest if you have a network lab of somekind that you download:
http://www.wireshark.org/
This will give you a real look at network traffic and how the different protocols work.
Cheers,
Edit: Btw i dont like E as an answer in this question. Simply because it say's serial port rather than ethernet port, serial port's do not have MAC addresses. Very odd.....DevOps Engineer and Security Champion. https://blog.pash.by - I am trying to find my writing style, so please bear with me. -
bearfan Member Posts: 70 ■■□□□□□□□□I got Wireshark and its very interesting.
Also, answer E should be "Ethernet" and not "Serial." That was a typo on my part. I changed it.
I'm scheduled to take the Intro test on July 23rd. I've been studying every day after work and on weekends, so I hope to be ready by then. -
Pash Member Posts: 1,600 ■■■■■□□□□□bearfan wrote:I got Wireshark and its very interesting.
Also, answer E should be "Ethernet" and not "Serial." That was a typo on my part. I changed it.
I'm scheduled to take the Intro test on July 23rd. I've been studying every day after work and on weekends, so I hope to be ready by then.
Good stuff, I wish you luck mate.
Cheers,DevOps Engineer and Security Champion. https://blog.pash.by - I am trying to find my writing style, so please bear with me.