Brocade Multi-Service IronWare Switching Configuration Guide (Supporting R05.6.00) - Manual (Page 851)

Multi-Service IronWare Switching Configuration Guide 821
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Configuring IP load sharing
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You can configure the Brocade device to forward BootP or DHCP requests. To do so, configure a
helper address on the interface that receives the client requests, and specify the BootP or DHCP
server’s IP address as the address you are helping the BootP or DHCP requests to reach. Instead of
the server’s IP address, you can specify the subnet directed broadcast address of the IP subnet the
server is in.
NOTE
The IP subnet configured on the port which is directly connected to the device sending a BootP or
DHCP request, does not have to match the subnet of the IP address given by the DHCP server.
BootP or DHCP forwarding parameters
The following parameters control the Brocade device’s forwarding of BootP or DHCP requests:
• Helper address – The BootP or DHCP server’s IP address. You must configure the helper
address on the interface that receives the BootP or DHCP requests from the client. The
Brocade device cannot forward a request to the server unless you configure a helper address
for the server.
• Gateway address – The Brocade device places the IP address of the interface that received the
BootP or 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 Brocade device 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 Brocade device to use.
• Hop Count – Each router that forwards a BootP or DHCP packet increments the hop count by 1.
Routers also discard a forwarded BootP or DHCP request instead of forwarding the request if
the hop count is greater than the maximum number of BootP or DHCP hops allowed by the
router. By default, the Brocade device forwards a BootP or 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 Brocade device will allow to a value from 1 – 15.
NOTE
The BootP or DHCP hop count is not the TTL parameter.
Configuring an IP helper address
The procedure for configuring a helper address for BootP or DHCP requests is the same as the
procedure for configuring a helper address for other types of UDP broadcasts. Refer to
“Configuring
an IP helper address” on page 820.
Changing the IP address used for stamping BootP or DHCP requests
When the Brocade device forwards a BootP or DHCP request, the Brocade device “stamps” the
Gateway Address field. The default value the Brocade device uses to stamp the packet is the
lowest-numbered IP address configured on the interface that received the request.
The BootP or DHCP stamp address is an interface parameter. Change the parameter on the
interface that is connected to the BootP or DHCP client.