9 Routing Fundamentals
This chapter covers
- How end hosts send IP packets to local and remote destinations
- The routing process
- How to read and interpret a router’s routing table
- Configuring static routes on a router
- How to use default routes to provide Internet connectivity
In this chapter we will cover routing - the process by which routers forward IP packets between networks. Specifically, we will cover elements of the following CCNA exam topics:
- 3.1 Interpret the components of routing table
- 3.2 Determine how a router makes a forwarding decision by default
- 3.3 Configure and verify IPv4 and IPv6 static routing
The term routing can actually refer to two different processes: the process by which routers build their routing table (a database of known destinations and how to forward packets toward them), and the process of actually forwarding packets. In this chapter we will cover both aspects of routing, and we will build upon this foundation in future chapters.
9.1 How end hosts send packets
Before we examine the details of how routers forward IP packets, let’s take a look at the end hosts that send those packets to each other. After a host prepares a packet to send to another host, it must encapsulate that packet in a frame; even though we are focusing on routing, a layer-3 process, do not forget about layer 2! Packets are never sent over the cable (or radio waves) without being encapsulated in a frame.