This chapter discusses some of the key issues involved in the design of network addressing models, the allocation of network addresses and names, and some of the techniques used to support a device configuration in medium- to large-scale internetworks. Since we are largely concerned with sizable networks, we will focus primarily on the IP address model, although we will briefly touch upon other addressing schemes that you may encounter. Network addressing is closely associated with routing design; hence, this chapter makes cross-references, as appropriate, to Chapter 3. The following topics are covered here:

• An overview of the IP addressing schemes in IP versions 4 and 6 and the function of unicast, multicast, and broadcast addresses. IP address and Autonomous System Number (ASN) registration, private addressing schemes, and Network Address Translation (NAT) are also discussed.

• Dynamic address and configuration services such as RARP, DHCP, and BOOTP.

• Name-to-address mapping and directory services DNS, WINS, X.500, LDAP.

• Commonly used design techniques for efficient addressing models, static and Variable Length Subnetting (VLSN), route summarization, Supernetting/Classless InterDomain Routing (CIDR).

Figure 2.1 illustrates some of the basic components of the overall IP architecture required for naming, addressing, and configuration services. As we can see in Figure 2.1, several layers of abstraction are introduced as we move up the stack. Address allocation and configuration are typically performed by DHCP or BOOTP. Address resolution (IP to MAC and vice versa) is performed by ARP and RARP. Unreachability is indicated via ICMP. Dynamic name services are provided via DNS.