CyberCertPrepNetwork FundamentalsNetwork DevicesEASYFree question
What is the role of ARP in a basic LAN communication, and why does a PC need to ARP before sending its first packet?
- A.Before a PC can send an Ethernet frame locally, it needs the destination's MAC address. ARP broadcasts 'who has IP x.x.x.x?' to all hosts. The owner replies with its MAC. The sender then constructs the Ethernet frame with the correct destination MAC
- B.ARP is only needed for internet communication, not local LAN
- C.ARP is performed by the switch automatically - the PC doesn't need to ARP
- D.ARP is only needed when the destination is on a different subnet
Why A is correct
Ethernet delivery requires MAC addresses. The IP stack knows the destination IP but not the MAC. ARP: PC broadcasts 'who has 192.168.1.5? Tell 192.168.1.10.' The device at .5 replies 'I'm at MAC xx:xx:xx:xx:xx:xx.' The sender caches this in its ARP table and uses the MAC for subsequent frames. For remote destinations, ARP is done for the default gateway's MAC instead.
Know someone studying for Network Fundamentals? Send them this one.