In addition, you can specify any UDP application by using the application UDP port number.
The
udp-port-num
parameter specifies the UDP application port number. If the application you want to enable is not listed above, enter
the application port number. You also can list the port number for any of the applications listed above.
To disable forwarding for an application, enter a command such as the following.
device(config)# no ip forward-protocol udp ntp
This command disables forwarding of SNMP requests to the helper addresses configured on Layer 3 switch interfaces.
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 unit 1, slot 1, port 2, enter the following commands.
device(config)# interface ethernet 1/1/2
device(config-if-1/1/2)# ip helper-address 1 10.95.7.6
The commands in this example change the CLI to the configuration level for port 1/1/2, then add a helper address for server 10.95.7.6
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.
By default, IP helper does not forward client broadcast request to a server within the network.
To forward a client broadcast request when the client and server are on the same network, configure an IP helper with unicast option on
the interface connected to the client.
To configure an IP helper unicast option on unit 1, slot 1, port 2, enter the following commands:
device(config)# interface 1/1/2
device(config-if-1/1/2)# ip helper-address 1 10.10.10.1 unicast
The IP helper with unicast parameter forwards the client request to the server 10.10.10.1 which is within the network.
Syntax:
ip helper-address
num
ip-addr
[unicast]
The
num
variable specifies the helper address number and can be from 1 through 16.
The
ip-addr
variable specifies the server IP address or the subnet directed broadcast address of the IP subnet the server is in.
The
unicast
parameter specifies that the client request must be forwarded to the server that is on the same network.
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.
Configuring IP parameters - Layer 3 switches
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