The IP Routing Process
The IP routing process is actually pretty simple, and it doesn’t change, regardless of the size of your network. I’m going to use Figure 9.2 to give you a picture of this step-by-step process. The question I’m asking is this: What happens when Host_A wants to communicate with Host_B on a different network? I’ll go through how to answer that question by breaking down the process with headings to make it easier to understand. First, check out Figure 9.2.
Figure 9.2 IP routing example using two hosts and one router
Suppose that a user on Host_A pings Host_B’s IP address. Routing doesn’t get any simpler than this, but it still involves a lot of steps. Let’s work through them.
- A packet is created on the host:
- Internet Control Message Protocol (ICMP) creates an echo request payload (which is just the alphabet in the data field).
- ICMP hands that payload to IP, which then creates a packet. At a minimum, this packet...
