1. Connecting Networks © 2004 Cisco Systems, Inc. All rights reserved. Exploring How IP Address Protocols Work INTRO v2.0—4-1

2. © 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—4-2 Outline Overview Address Resolution Protocol ARP Table Automated Ways of Getting an IP Address Domain Name System Summary

3. © 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—4-3 ARP

4. © 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—4-4 ARP Table

5. © 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—4-5 DHCP

6. © 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—4-6 DNS Application specified in the TCP/IP suite Means to translate human-readable names into IP addresses

7. © 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—4-7 Summary ARP is used to map (bind) an IP addresses to its corresponding physical MAC addresses. To forward a packet from one host to another host on the same network over an Ethernet connection, each host maintains an ARP table (or ARP cache). The ARP table is used to mat the destination IP address to the destination physical MAC address. DHCP is used to assign IP addresses automatically and also other TCP/IP stack configuration parameters such as the subnet mask and default router and DNS servers.

8. © 2004 Cisco Systems, Inc. All rights reserved. INTRO v2.0—4-8 Summary (Cont.) A network device can use BOOTP when it starts up to obtain an IP address. With RARP, a physical address, such as a MAC address, can be associated with an IP address. DNS is an application that is specified in the TCP/IP suite, providing a means to translate human-readable names into IP addresses.