Brocade BigIron RX Series Configuration Guide - Manual (Page 298)

220 BigIron RX Series Configuration Guide
53-1002484-04
Configuring forwarding parameters
7
Configuring an IP helper address
To forward a client’s broadcast request for a UDP application when the client and server are on
different networks, you must configure a helper address on the interface connected to the client.
Specify the server’s IP address or the subnet directed broadcast address of the IP subnet the
server is in as the helper address.
You can configure up to 16 helper addresses on each interface. You can configure a helper
address on an Ethernet port or a virtual interface.
To configure a helper address on interface 2 on device module 1, enter the following commands.
BigIron RX(config)# interface e 1/2
BigIron RX(config-if-e1000-1/2)# ip helper-address 207.95.7.6
The commands in this example change the CLI to the configuration level for port 1/2, then add a
helper address for server 207.95.7.6 to the port. If the port receives a client request for any of the
applications that the device is enabled to forward, the device forwards the client’s request to the
server.
Syntax: ip helper-address <ip-addr>
The <ip-addr> command specifies the server’s IP address or the subnet directed broadcast
address of the IP subnet the server is in.
Configuring BootP/DHCP forwarding parameters
The DHCP relay will allow for IP address grants that do not match the subnets configured on the
interface that the DHCP request was received. A host on an IP network can use BootP/DHCP to
obtain its IP address from a BootP/DHCP server. To obtain the address, the client sends a
BootP/DHCP request. The request is a subnet directed broadcast and is addressed to UDP port 67.
A limited IP broadcast is addressed to IP address 255.255.255.255 and is not forwarded by the
device or other IP routers.
When the BootP/DHCP client and server are on the same network, the server receives the
broadcast request and replies to the client. However, when the client and server are on different
networks, the server does not receive the client’s request, because the device does not forward the
request.
You can configure the device to forward BootP/DHCP requests. To do so, configure a helper
address on the interface that receives the client requests, and specify the BootP/DHCP server’s IP
address as the address you are helping the BootP/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/DHCP request, does not have to match the subnet of the IP address given by the DHCP server.
BootP/DHCP forwarding parameters
The following parameters control the device’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 device cannot
forward a request to the server unless you configure a helper address for the server.