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Configuring IP
BootP/DHCP Forwarding Parameters
The following parameters control the routing switch’s forwarding of BootP/DHCP requests:
• Helper address – The BootP/DHCP server’s IP address. You must configure the helper address on the
interface that receives the BootP/DHCP requests from the client. The routing switch cannot forward a request
to the server unless you configure a helper address for the server.
• Gateway address – The routing switch places the IP address of the interface that received the BootP/DHCP
request in the request packet’s Gateway Address field (sometimes called the Router ID field). When the
server responds to the request, the server sends the response as a unicast packet to the IP address in the
Gateway Address field. (If the client and server are directly attached, the Gateway ID field is empty and the
server replies to the client using a unicast or broadcast packet, depending on the server.)
By default, the routing switch uses the lowest-numbered IP address on the interface that receives the request
as the Gateway address. You can override the default by specifying the IP address you want the routing
switch to use.
• Hop Count – Each router that forwards a BootP/DHCP packet increments the hop count by 1. Routers also
discard a forwarded BootP/DHCP request instead of forwarding the request if the hop count is greater than
the maximum number of BootP/DHCP hops allows by the router. By default, an HP ProCurve routing switch
forwards a BootP/DHCP request if its hop count is four or less, but discards the request if the hop count is
greater than four. You can change the maximum number of hops the routing switch will allow to a value from
1 – 15.
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 6-69.
Changing the IP Address Used for Stamping BootP/DHCP Requests
When the routing switch forwards a BootP/DHCP request, the routing switch “stamps” the Gateway Address field.
The default value the routing switch uses to stamp the packet is the lowest-numbered IP address configured on
the interface that received the request. If you want the routing 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.
USING THE CLI
To change the IP address used for stamping BootP/DHCP requests received on interface 1/1, enter commands
such as the following:
HP9300(config)# int e 1/1
HP9300(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 routing switch will place this IP address in the
Gateway Address field of BootP/DHCP requests that the routing switch receives on port 1/1 and forwards to the
BootP/DHCP server.
Syntax: ip bootp-gateway <ip-addr>
USING THE WEB MANAGEMENT INTERFACE
You cannot change the IP address used for stamping BootP/DHCP requests using the Web management
interface.
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