Configuring an ip helper address – Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide User Manual
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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 Layer 3 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 Layer 3 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, a
Brocade Layer 3 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
Layer 3 switch will allow to a value from 1 through 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. Refer to
Configuring the BOOTP and DHCP reply source address
You can configure the Brocade device so that a BOOTP/DHCP reply to a client contains the server IP
address as the source address instead of the router IP address. To do so, enter the following
command at the Global CONFIG level of the CLI.
device(config)# ip helper-use-responder-ip
Syntax: [no] ip helper-use-responder-ip
Changing the IP address used for stamping BootP and 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.
device(config)# interface ethernet 1/1
device(config-if-1/1)# ip bootp-gateway 10.157.22.26
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 10.157.22.26. 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.
Configuring an IP helper address
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FastIron Ethernet Switch Layer 3 Routing Configuration Guide
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