Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 79)

Advertisement message from the Layer 3 switch, the host resets the hold time for the Layer 3 switch to
the hold time specified in the new advertisement. If the hold time of an advertisement expires, the host
discards the advertisement, concluding that the router interface that sent the advertisement is no longer
available. The value must be greater than the value of the maxadvertinterval parameter and cannot be
greater than 9000. The default is three times the value of the maxadvertinterval parameter.
The maxadvertinterval parameter specifies the maximum amount of time the Layer 3 switch waits
between sending Router Advertisements. You can specify a value from 1 to the current value of the
holdtime parameter. The default is 600 seconds.
The minadvertinterval parameter specifies the minimum amount of time the Layer 3 switch can wait
between sending Router Advertisements. The default is three-fourths (0.75) the value of the
maxadvertinterval parameter. If you change the maxadvertinterval parameter, the software
automatically adjusts the minadvertinterval parameter to be three-fourths the new value of the
maxadvertinterval parameter. If you want to override the automatically configured value, you can
specify an interval from 1 to the current value of the maxadvertinterval parameter.
The preferencenumber parameter specifies the IRDP preference level of this Layer 3 switch. If a host
receives Router Advertisements from multiple routers, the host selects the router interface that sent the
message with the highest interval as the host default gateway. The valid range is from 0 to
4294967296. The default is 0.
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):
Reverse Address Resolution Protocol configuration
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