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The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  TCP/IP Network Configuration and Management Protocols (BOOTP, DHCP, SNMP and RMON)            9  Host Configuration and TCP/IP Host Configuration Protocols (BOOTP and DHCP)                 9  TCP/IP Dynamic Host Configuration Protocol (DHCP)                      9  DHCP Client/Server Implementation, Features and Issues

DHCP Message Relaying and BOOTP Relay Agents 1 2 3 DHCP Server Conflict Detection

APIPA Limitations

Bear in mind that APIPA is not a proper replacement for full DHCP. The 169.254.0.0/16 block is a private IP range and comes with all the limitations of private IP addresses, including inability to use these addresses on the Internet. Also, APIPA cannot provide the other configuration parameters that a client may need to get from a DHCP server. Finally, APIPA will not work properly in conjunction with proxy ARP, because the proxy will respond for any of the private addresses, so they will all appear to be used.

Since it uses ARP to check for address conflicts, APIPA is not well-suited for large internetworks. To use it on an internetwork with multiple subnets, you would require software that allows each subnet to use a different portion of the full 169.254.0.0/16 blocks, to avoid conflicts. In practice, APIPA is a solution for small networks; large internetworks deal with the problem of not being able to contact a DHCP server by making sure that a client can always contact a DHCP server. J

DHCP Message Relaying and BOOTP Relay Agents 1 2 3 DHCP Server Conflict Detection