Routing – use case

The purpose of a router is to connect networks together, whether it be internal subnets or external networks and route packets between them. A router sits at layer 3 of the OSI Reference Model, where the data packets are known as IP packets, as Layer 3 of the OSI deals with IP addressing and delivery.

If we look at Figure 25, we can see five different routers that connect networks between New York, Dublin, Paris, London, and Edinburgh:

Figure 25: Routing packets.

If we think of these routers as post offices delivering mail, it may make it easier to understand. If mail arrives at the Paris post office, the people working ...

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