2.2 Address mapping and configuration techniques

In large internetworks automating address allocation and device configuration is a must. Long gone are the days when network administrators hand-crafted every single host; today's internetworks are simply too large and too dynamic to make this either practical or economical. For example, a workstation typically needs the following items resolved at boot time:

• IP address and subnet mask (a basic requirement for any form of IP communication)

• Host name, domain name, DNS server name (covered in section 2.3)

• Default gateway (i.e., the nearest router)

• Primary and secondary DNS server

• Primary and secondary WINS server address (for Microsoft networks)

• Boot image (if the workstation has no local persistent storage capability)

At the very least a workstation needs an IP address and subnet mask, together with knowledge of how to reach the nearest router; otherwise, communication over an IP network is not practical. Today there are several protocols and services that are widely used to assist with address allocation, booting, and device configuration. These include ARP, RARP, Proxy ARP, BOOTP, and DHCP. Another important protocol used to indicate errors with their operations is ICMP. We will discuss these protocols in turn.