In addition, you can specify any UDP application by using the application UDP port number.
The udp-port-num parameter species 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
congured on Layer 3 switch interfaces.
Conguring an IP helper address
To forward a client broadcast request for a UDP application when the client and server are on dierent networks, you must congure 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 congure up to 16 helper addresses on each interface. You can congure a helper address on an Ethernet port or a virtual
interface.
To congure 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 conguration 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, congure an IP helper with unicast option on
the interface connected to the client.
To congure 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
species the helper address number and can be from 1 through 16.
The ip-addr variable species the server IP address or the subnet directed broadcast address of the IP subnet the server is in.
The unicast parameter species that the client request must be forwarded to the server that is on the same network.
BootP and DHCP relay parameter conguration
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 dierent networks, the server does not receive the client request, because the Layer 3 switch
does not forward the request.
Conguring IP parameters - Layer 3 switches
FastIron Ethernet Switch Layer 3 Routing
82 53-1003627-04
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