Foundry Networks Switch and Router, Installation And Configuration Manual, Page: 510 / 1070

Foundry Switch and Router Installation and Configuration Guide
15 - 68 December 2000
USING THE WEB MANAGEMENT INTERFACE
You cannot configure these options using the Web management interface.
Configuring RARP
The Reverse Address Resolution Protocol (RARP) provides a simple mechanism for directly-attached IP hosts to
boot over the network. RARP allows an IP host that does not have a means of storing its IP address across power
cycles or software reloads to query a directly-attached router for an IP address.
RARP is enabled by default. However, you must create a RARP entry for each host that will use the Layer 3
Switch for booting. A RARP entry consists of the following information:
• The entry number – the entry’s sequence number in the RARP table.
• The MAC address of the boot client.
• The IP address you want the Layer 3 Switch to give to the client.
When a client sends a RARP broadcast requesting an IP address, the Layer 3 Switch responds to the request by
looking in the RARP table for an entry that contains the client’s MAC address:
• If the RARP table contains an entry for the client, the Layer 3 Switch sends a unicast response to the client
that contains the IP address associated with the client’s MAC address in the RARP table.
• If the RARP table does not contain an entry for the client, the Layer 3 Switch silently discards the RARP
request and does not reply to the client.
How RARP Differs from BootP/DHCP
RARP and BootP/DHCP are different methods for providing IP addresses to IP hosts when they boot. These
methods differ in the following ways:
• Location of configured host addresses
• RARP requires static configuration of the host IP addresses on the Layer 3 Switch. The Layer 3 Switch
replies directly to a host’s request by sending an IP address you have configured in the RARP table.
• The Layer 3 Switch forwards BootP and DHCP requests to a third-party BootP/DHCP server that
contains the IP addresses and other host configuration information.
• Connection of host to boot source (Layer 3 Switch or BootP/DHCP server):
• RARP requires the IP host to be directly attached to the Layer 3 Switch.
• An IP host and the BootP/DHCP server can be on different networks and on different routers, so long as
the routers are configured to forward (“help”) the host’s boot request to the boot server.
• You can centrally configure other host parameters on the BootP/DHCP server, in addition to the IP
address, and supply those parameters to the host along with its IP address.
To configure the Layer 3 Switch to forward BootP/DHCP requests when boot clients and the boot servers are on
different sub-nets on different Layer 3 Switch interfaces, see “Configuring BootP/DHCP Forwarding Parameters”
on page 15-73.
Disabling RARP
RARP is enabled by default. If you want to disable the feature, you can do so using either of the following
methods.
USING THE CLI
To disable RARP, enter the following command at the global CONFIG level:
BigIron(config)# no ip rarp
Syntax: [no] ip rarp
To re-enable RARP, enter the following command:
BigIron(config)# ip rarp