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Which entry will be in the ARP cache of HostA to support this transmission?

Refer to the exhibit. After HostA pings HostB, which entry will be in the ARP cache of HostA to support this transmission?

 

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A image
B image
C image
D image
E image
F image



Answer : D

Explanation:

ARP – Address Resolution Protocol
It is used to find the MAC address from known IP address.
ARP is used to convert an IP address to a physical address such as an Ethernet address (MAC Address).

If a host or device transmitting data to another network (not same IP subnet), then data will forward to default gateway.

In the exhibit, the Host A is transmitting data to Host B, then Host A forward the packet to Router1, for that communication Host A needs MAC address of Router1. If we check the ARP cache of Host A, we will get 192.168.6.1 – 000f.2480.8916.

Download the topology and check it for your own: https://app.box.com/s/hzyjmaxrjjegm3zac9xo

Screenshots

image

Click HostA > Desktop > Command Prompt

Commands

arp -a used to view the arp cache
ping 192.168.4.7 used to check the connectivity to HostB


image

Comments

  1. Thanks a lot for explaining. Please share the other answer that I have asked asap :)

    ReplyDelete
  2. I saw an answer to this question in a ccna dump as A and not D. A bit not clear. Please enlighten me. Thanks

    ReplyDelete
  3. I saw an answer to this question in a ccna dump as A and not D. A bit not clear. Please enlighten me. Thanks

    ReplyDelete
  4. I think this is the right answer

    ReplyDelete
  5. What host A would do is:
    – Host A knew that the IP address of host B is not in the same subnet so it would send the ICMP message (or ping) to default gateway which is 192.168.6.1 (fa0/0). However, it needs to know the actually physical address of this IP address to do so.
    – To get the MAC address host A will send ARP request (broadcast) with the IP address 192.168.6.1 as destination. F0/0 gets it and send back the MAC address. THIS MAC ADDRESS and the IP address 192.168.6.1 of F0/0 will be recorded in ARP cache of host A for future use.

    ReplyDelete
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    ReplyDelete
  7. Thank you, I also did the sim in packet tracert and indeed is the router what appears in arp -a. Dump is wrong. Thanks

    ReplyDelete
  8. It is easy to test it on Packet Tracer and observe that the correct answer is D.

    192.168.6.1 000f.2480.8916 dynamic

    ReplyDelete

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