DHCP Host A Server DNS Host B EE Server User on Host Auses the wel-known ping pr
ID: 3824701 • Letter: D
Question
DHCP Host A Server DNS Host B EE Server User on Host Auses the wel-known ping programto ping the lP address of Host B. (In this case suppose the user knows the IP address of the destination they want to ping)The ping utility will request the ICMPlayer to send an ICMP Echo Request to the destination lP address. Given the network topology above what are the values of the fields in the various network headers o the ICMP packet when it is sent. How does the host know this information? (Note some information is hard-coded, some information is determined by the protocol, or has standard "well-known" or default values, andother fields are dynamically learnedvia some protocol. Indicate which fields fall into which category, and if dynamically learned, specify the protocol) CMP Header: Message Code: Message Type: P Header: Source IP: Destination IP: Time to live: Encapsulated Protocol: Ethernet Header: Destination MAC: Source MAC: Encapsulated Protocol:Explanation / Answer
Host A:
IP: 10.0.0.97
MAC: 24:29:9C:E0:FF:55
Host B:
IP: 10.0.0.3
MAC: CC:49:CE:D0:A8:70
ICMP Header:
Message Code: 0 (Message code 0 is for ping request)
Message Type: 0 (Message type 0 is for ping request)
IP Header:
Source IP: 10.0.0.97
Destination IP: 10.0.0.3
Time-to-live: 30 (Default Value)
Encapsulated Protocol: UDP
Ethernet Header:
Destination MAC: 24:29:9C:E0:FF:55
Source MAC: CC:49:CE:D0:A8:70 (Target host is on same network. So sender can get the MAC address using ARP call and use it in the Ethernet Header)
Encapsulated Protocol: UDP
If the user now ping DNS server using IP address:
ICMP Header:
There is no change in ICMP header. Because Message code and Message types are still same for nodes of same network or different network.
IP header:
This would be changed. Destination IP would be the IP address of DNS server.
Ethernet Header:
Destination MAC would be blank. Because the target node is on a different network. ARP cannot get the hardware address from a different network.
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