UDP Helper Configuration 303To delete this feature, enter:system-view[SW5500]acl number 2500[SW5500-acl-basic-2500]undo rule 0UDP HelperConfigurationThis section contains UDP Helper configuration information.Overview of UDP Helper The major function of the UDP Helper is to relay-forward UDP broadcast packets, thatis, it can convert UDP broadcast packets into unicast packets and send them to thedesignated server, as a relay.When UDP Helper starts, the Switch can judge whether to forward the UDP broadcastpackets received at the port based on UDP port ID. If yes, the Switch then modifiesthe IP address in the IP packet header and sends the packet to the designateddestination server. Otherwise, it sends the packet to the upper layer module forfurther processing. For the BOOTP/DHCP broadcast packet, if the client specifies inthe request message that the response message needs to be received as broadcastpacket, then the Switch broadcasts the response message to the client. Otherwise, itunicasts the response message.UDP HelperConfigurationUDP Helper configuration includes:■ Enabling/Disabling UDP Helper Function■ Configuring UDP Port with Replay Function■ Configuring the Relay Destination Server for Broadcast PacketEnabling/Disabling UDP Helper FunctionWhen the UDP Helper function is enabled, you can configure the UDP ports whereUDP function is required and the relay function is enabled at UDP ports 69, 53, 37,137, 138, and 49. When the function is disabled, the relay function configured at allUDP ports, including the default six ports, is disabled.Perform the following configuration in System View.By default, the UDP Helper function is disabled.Configuring UDP Port with Replay FunctionWhen the UDP relay function is enabled, by default the system forwards thebroadcast packets on the UDP ports listed in Table 300. You can configure up to 256UDP ports with the relay function.Table 299 Enabling/Disabling UDP Helper functionOperation CommandEnable UDP Helper function udp-helper enableDisable UDP Helper function undo udp-helper enableTable 300 Default UDP Ports ListProtocol UDP port IDTrivial File Transfer Protocol (TFTP) 69Domain Name System (DNS) 53Time service 37
