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 server's IP subnet 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.
  1. Enter the global configuration mode by issuing the configure terminal command.
    device# configure terminal
  2. Enter the interface configuration mode.
    device(config)# interface ethernet 1/1/2
  3. Add a helper address for the server.
    device(config-if-1/1/2)# ip helper-address 1 10.95.7.6
    The commands in the example above 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.
  4. By default, an IP helper does not forward client broadcast requests 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 the unicast option on the interface connected to the client.
    device(config-if-1/1/2)# ip helper-address 1 10.10.10.1 unicast
    The previous example configures an IP helper unicast option on unit 1, slot 1, port 2. The IP helper with unicast parameter forwards the client request to the server 10.10.10.1, which is within the network.