|  |  | Summary

This chapter discussed routing and addressing as it relates to the network layer of the OSI model. You learned that:

- internetworking functions of the network layer include network addressing and best path selection for traffic.
- there are two addressing methods: flat and hierarchical.
- there are three classes of IP addresses that an organization can receive from InterNIC: Class A, B, and C.
- InterNIC reserves Class A addresses for governments throughout the world, Class B addresses for medium-size companies, and Class C addresses for all other entities
- when written in a binary format, the first bit of a Class A address is always 0
- the first 2 bits of a Class B address are always 10, and the first 3 bits of a Class C address are always 110
- in order to provide extra flexibility for the network administrator, networks --- particularly large ones --- are often divided into smaller networks called subnetworks or subnets
- subnets are concealed from outside networks by using masks referred to as subnet masks

In the next chapter, you will see how devices and routing protocols operate at the network layer.