Foundry Configuration Guide for the FESX, FSX, and FWSX
16 - 50 © Foundry Networks, Inc. December 2005
NOTE: The BootP/DHCP hop count is not the TTL parameter.
Configuring an IP Helper Address
The procedure for configuring a helper address for BootP/DHCP requests is the same as the procedure for
configuring a helper address for other types of UDP broadcasts. See “Configuring an IP Helper Address” on
page 16-49.
Changing the IP Address Used for Stamping BootP/DHCP Requests
When the Layer 3 Switch forwards a BootP/DHCP request, the Layer 3 Switch “stamps” the Gateway Address
field. The default value the Layer 3 Switch uses to stamp the packet is the lowest-numbered IP address
configured on the interface that received the request. If you want the Layer 3 Switch to use a different IP address
to stamp requests received on the interface, use either of the following methods to specify the address.
The BootP/DHCP stamp address is an interface parameter. Change the parameter on the interface that is
connected to the BootP/DHCP client.
To change the IP address used for stamping BootP/DHCP requests received on interface 1/1, enter commands
such as the following:
FastIron SuperX Router(config)# int e 1/1
FastIron SuperX Router(config-if-1/1)# ip bootp-gateway 109.157.22.26
These commands change the CLI to the configuration level for port 1/1, then change the BootP/DHCP stamp
address for requests received on port 1/1 to 192.157.22.26. The Layer 3 Switch will place this IP address in the
Gateway Address field of BootP/DHCP requests that the Layer 3 Switch receives on port 1/1 and forwards to the
BootP/DHCP server.
Syntax: ip bootp-gateway <ip-addr>
Changing the Maximum Number of Hops to a BootP Relay Server
Each BootP/DHCP request includes a field Hop Count field. The Hop Count field indicates how many routers the
request has passed through. When the Layer 3 Switch receives a BootP/DHCP request, the Layer 3 Switch looks
at the value in the Hop Count field.
• If the hop count value is equal to or less than the maximum hop count the Layer 3 Switch allows, the Layer 3
Switch increments the hop count by one and forwards the request.
• If the hop count is greater than the maximum hop count the Layer 3 Switch allows, the Layer 3 Switch
discards the request.
To change the maximum number of hops the Layer 3 Switch allows for forwarded BootP/DHCP requests, use
either of the following methods.
NOTE: The BootP/DHCP hop count is not the TTL parameter.
To modify the maximum number of BootP/DHCP hops, enter the following command:
FESX424 Router(config)# bootp-relay-max-hops 10
This command allows the Layer 3 Switch to forward BootP/DHCP requests that have passed through up to ten
previous hops before reaching the Layer 3 Switch.
Syntax: bootp-relay-max-hops <1-15>
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