Configuration Guide User guide

FastIron Configuration Guide 1011
53-1002494-02
Configuring IP parameters – Layer 3 Switches
Configuring an IP helper address
To forward a client 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 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 chassis module 1, enter the following commands.
Brocade(config)# interface ethernet 1/2
Brocade(config-if-1/2)# ip helper-address 1 207.95.7.6
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 Layer 3 Switch is enabled to forward, the Layer 3 Switch forwards the client
request to the server.
Syntax: ip helper-address <num> <ip-addr>
The <num> parameter specifies the helper address number and can be from 1 through 16.
The <ip-addr> command specifies the server IP address or the subnet directed broadcast address
of the IP subnet the server is in.
BootP and DHCP relay parameter configuration
A host on an IP network can use BootP or DHCP to obtain its IP address from a BootP/DHCP server.
To obtain the address, the client sends a BootP or 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 Brocade Layer 3 Switch or other IP routers.
When the BootP or 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 request, because the Layer 3 Switch does not
forward the request.
You can configure the Layer 3 Switch 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 IP address as the address you are helping the BootP/DHCP requests to reach. Instead of
the server IP address, you can specify the subnet directed broadcast address of the IP subnet the
server is in.
BootP and DHCP relay parameters
The following parameters control the Layer 3 Switch forwarding of BootP and DHCP requests:
• Helper address – The BootP/DHCP server IP address. You must configure the helper address
on the interface that receives the BootP/DHCP requests from the client. The Layer 3 Switch
cannot forward a request to the server unless you configure a helper address for the server.