A router connects a home network to the internet.
Explain how a router uses the destination IP address in a packet header.
Mark scheme
Award up to two marks for a linked explanation such as:
- The router reads the destination IP address (1) so it knows which network/device the packet is for (1)
- The router looks up the destination IP address in its routing table (1) to find the next router/route for the packet (1)
- The router forwards the packet to the next router (1) that leads towards that IP address / is on the best route (1)
For both marks, the expansion must follow/associate with the statement.
Do not accept MAC address - routers use the IP address to route packets between networks.
Do not accept 'it finds the exact device' without saying how the router uses the address, e.g. routing table/next router.
Example answers and how they were marked
The router looks up the destination IP address in its routing table to find the next router to send the packet to.
Why: Linked point (1) and reason (1): looks up the destination IP address in the routing table to find the next router.
It reads the destination IP address.
Why: Reads the destination IP address (1) but gives no linked reason about a routing table or next router.
It reads the MAC address so it knows which computer sent the packet.
Why: Routers use the IP address to route packets, not the MAC address; no creditworthy point.