ITPEC FE Morning October 2018 Question 32
ITPEC FE Morning October 2018 — Question 32 of 80
Router Packet Forwarding — a router uses the destination IP address to route packets.
A router operates at Layer 3 (Network layer) and makes forwarding decisions based on the destination IP address in the packet header.
- •Router looks up the destination IP in its routing table
- •Finds the best matching route (longest prefix match)
- •Forwards the packet to the appropriate interface/next hop
- •Rewrites MAC addresses at each hop (Layer 2 info changes, Layer 3 stays)
Why not others:
- (b) Destination MAC address — used by switches (Layer 2), not routers
- (c) Source IP address — identifies the sender, not the destination
- (d) Source MAC address — identifies the previous hop's interface, irrelevant for routing
Key rule: Routers = IP (Layer 3), Switches = MAC (Layer 2).
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