The IP Routing Process

The IP routing process is fairly simple and doesn’t change, regardless of the size of your network. For an example, we’ll use Figure 8-2 to describe step-by-step what happens when Host_A wants to communicate with Host_B on a different network.

Figure 8-2: IP routing example using two hosts and one router


In this example, a user on Host_A pings Host_B’s IP address. Routing doesn’t get simpler than this, but it still involves a lot of steps. Let’s work through them:

1. Internet Control Message Protocol (ICMP) creates an echo request payload (which is just the alphabet in the data field).

2. ICMP hands that payload to Internet ...

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