The routing process is simple; it does not matter how small or large your network is. With that said, we are speaking of IPv4. Because in IPv4 we have ARP that must happen in the first time around and in IPv6 that does not exist. But we will talk about that later in the book.
So, using the same three-router topology, we get the following diagram:
If PC0 wants to communicate with any PC outside its own network, it must go through the default gateway. There are a couple of things that need to be known to the network:
- Layer 3 source address
- Layer 3 destination address
- Layer 2 source address
- Layer 2 destination address
- Source port number (chosen randomly, ports above 1024)
- Destination port number (depends on the protocol you are using—Telnet, SSH, HTTP, and so on)
Once this information is known, the packet can go to the router and be forwarded to its...