You Can't Just Send Data; You Have to Send a Frame

You Can't Just Send Data; You Have to Send a Frame

You can't just send end user data, such as the contents of a web page, over an Ethernet. The thing that is actually sent over the Ethernet is an Ethernet frame. Inside the frame, after the other various headers, is the true end user data. In this section, you learn how to build a frame that is appropriate for a WAN serial link between two routers.

In Figure 14-5, when Hannah sends a packet to the www.example.com web server at IP address 150.1.3.3, she sends the IP packet to her default gatewaynamely, R1. When R1 receives the Ethernet frame, it checks to see whether errors occurred. If errors did not occur, R1 extracts the IP packet and begins the process of making a routing decision.

Figure 14-6 picks up the routing process at this point. R1 has the packet with destination address 150.1.3.3. That destination address matches the route for subnet 150.1.3.0, which lists outgoing interface Serial0 and next-hop IP address 150.1.2.2, which is R2's IP address.