Router – Why do routers have only a few interfaces

interfaceroutersubnetvlan

Why do routers have only a few interfaces? Since one router interface is one subnet itself, a router given G0/0, G0/1 and G0/2 can only have three subnets.

Is it sustainable? How can we go beyond three subnets, or is this where VLAN plays a part?

Best Answer

You forget that routers can have virtual interfaces. For example, you can create GigbitEthernet0/0.10. You can have many, many different VLANs, each with its own network, on virtual interfaces of a single physical interface.

Routers only need to terminate the layer-2 LANs. It is the LANs that really need a lot of interfaces, so you use switches for the LAN interfaces, and the switch connects to the router (with a trunk if you have more than one VLAN).

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