ITPEC FE Morning October 2023 Question 30
Which of the following is the most appropriate information for a router to determine the destination of an incoming packet?
Explanation
Destination IP address — a router works at the network layer and forwards by looking up where the packet is going.
For each incoming packet the router reads the destination IP address from the IP header, finds the best matching route in its routing table, and sends the packet to the next hop. MAC addresses only identify devices on one link, and are rewritten at every router hop.
Answer (a)
Why not others:
- •(b) Destination MAC address — what a layer 2 switch uses; at a router it only addresses the router itself on the incoming link
- •(c) Source IP address — tells where the packet came from, not where it should go
- •(d) Source MAC address — identifies the previous device on the local link, and is useless for choosing a route
Key rule: Routers forward by destination IP address (layer 3); switches forward by destination MAC address (layer 2).
Networks · AI-written, may contain errors
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