Assume the following two scenarios –
1. A PC with IP address 192.168.1.2 with subnet mask tries to access a PC with IP address 192.168.2.1 with subnet mask 255.255.255.0.
2. A PC with private IP address 192.168.1.2 with subnet mask 255.255.255.0 tries to access a website on the internet.
In scenario 1, the PC’s are on different networks. In scenario 2, the PC is trying to access a website, which is on the internet, again on a different network. In both the cases, the destination addresses are on different networks. When two systems wishes to communicate and they are on different IP networks, a gateway device is required. A gateway device, in simple terms is a layer 3 device, which is capable of forwarding IP packets. The common misconception is that the gateway device needs to be a router. This is not true. A gateway device can be a Windows server operating system which has the routing service. A linux operating system can also act as a gateway device.
The above content is a sample preview from the Ebook
Routing & Switching Fundamentals