Information Technology Reference
In-Depth Information
Proxy-ARP Example
Figure 6-12
Host B
IP: 192.168.2.20
MAC: 0010.a070.1103
IP1: 192.168.1.2
IP2: 192.168.2.2
MAC: 00c0.a070.34a0
Step 1
Step 2
Host A
IP: 192.168.1.22
MAC: 0010.a070.0102
BOOTP
BOOTP was first defined in RFC 951 and has been updated by RFC 1395, RFC 1497, RFC
1532, and RFC 1542. BOOTP is a protocol that allows a booting host to configure itself by
dynamically obtaining its IP address, IP gateway, and other information from a remote server.
You can use a single server to centrally manage numerous network hosts without having to
configure each host independently.
BOOTP is an application layer-based protocol that uses UDP/IP protocols for transport. UDP
port 67 sends BOOTP requests to the BOOTP server, and the server uses UDP port 68 to send
messages to the UDP client. The destination IP of the BOOTP requests uses the all-hosts
(255.255.255.255), which are not forwarded by the router. If the BOOTP server is one or more
router hops from the subnet, the local default gateway router must be configured to forward the
BOOTP requests.
The interface command
ip helper-address
x.x.x.x
is configured on interfaces with workstations
that acquire their IP address information using BOOTP. The
ip helper-address
command
changes the destination IP address of the BOOTP request and forwards it to the configured
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