RARP, BOOTP, and DHCP
The ARP and proxy ARP processes both action afterwards a host knows its IP abode and subnet mask.
RARP, BOOTP, and DHCP represent the change of protocols authentic to advice a host dynamically
learn its IP address. All three protocols crave the applicant host to accelerate a advertisement to begin
discovery, and all three await on a server to apprehend the appeal and accumulation an IP abode to the client.
Figure 5-2 shows the basal processes with RARP and BOOTP.
RARP and BOOTP—Basic Processes
A RARP appeal is a host’s attack to acquisition its own IP address. So RARP uses the aforementioned old ARP
message, but the ARP appeal lists a MAC abode ambition of its own MAC abode and a ambition IP
address of 0.0.0.0. A preconfigured RARP server, which charge be on the aforementioned subnet as the client,
receives the appeal and performs a table lookup in its configuration. If that ambition MAC address
listed in the ARP appeal is configured on the RARP server, the RARP server sends an ARP reply,
after entering the configured IP abode in the Source IP abode field.
BOOTP was authentic in allotment to advance IP abode appointment appearance of RARP. BOOTP uses a
completely altered set of messages, authentic by RFC 951, with the commands encapsulated
inside an IP and UDP header. With the actual router configuration, a router can advanced the
BOOTP packets to added subnets—allowing the deployment of a centrally amid BOOTP server.
Also, BOOTP supports the appointment of abounding added tidbits of information, including the subnet
mask, absence gateway, DNS addresses, and its namesake, the IP abode of a cossack (or image)
server. However, BOOTP does not break the agreement accountability of RARP, still acute that the
server be preconfigured with the MAC addresses and IP addresses of anniversary client.
RARP Broadcast
2 RARP Reply
MAC
0200.1111.1111 10.1.1.1
0200.1234.5678 10.1.1.2
0200.5432.1111 10.1.1.3
RARP Configuration
Your IP Abode Is
10.1.1.1
RARP Server
2
Hannah
IP: ?.?.?.?
MAC: 0200.1111.1111
MAC IP Gateway
0200.1111.1111 10.1.1 . 1
0200.1234.5678 10.1.1 . 2
0200.5432.1111 10.1.1.3
10.1.1.200
10.1.1.200
10.1.1.200
Hey Everybody! My MAC Abode Is
0200.1111.1111. If You Are a BOOTP
Server, Please Tell Me My IP Address!
1
1 BOOTP Broadcast
2 BOOTP Reply
Configuration
10.1.1.200
BOOTP
Your IP Abode Is 10.1.1.1
Your Absence Aperture Is 10.1.1.200