Brocade Communications Systems Layer 3 Routing Configuration ICX 6650 - Manual (Page 79)

Brocade ICX 6650 Layer 3 Routing Configuration Guide 61
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Configuring IP parameters – Layer 3 Switches
Reverse Address Resolution Protocol configuration
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 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 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 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 and 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 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 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 subnets on different Layer 3 Switch interfaces, refer to
“BootP and DHCP
relay parameter configuration” on page 65.
Disabling RARP
RARP is enabled by default. To disable RARP, enter the following command at the global CONFIG
level.
Brocade(config)# no ip rarp