Operation Manual – UDP HelperH3C S5500-EI Series Ethernet Switches Chapter 1 UDP Helper Configuration1-1Chapter 1 UDP Helper ConfigurationWhen configuring UDP Helper, go to these sections for information you are interestedin:z Introduction to UDP Helperz Configuring UDP Helperz Displaying and Maintaining UDP Helperz UDP Helper Configuration Example1.1 Introduction to UDP HelperSometimes, a host needs to forward broadcasts to obtain network configurationinformation or request the names of other devices on the network. However, if theserver or the device to be requested is located in another broadcast domain, the hostcannot obtain such information through broadcast.To solve this problem, the device provides the UDP Helper function to relay specifiedUDP packets. In other words, UDP Helper functions as a relay agent that converts UDPbroadcast packets into unicast packets and forwards them to a specified destinationserver.With UDP Helper enabled, the device decides whether to forward a received UDPbroadcast packet according to the UDP destination port number of the packet.z If the destination port number of the packet matches the one pre-configured on thedevice, the device modifies the destination IP address in the IP header, and thensends the packet to the specified destination server.z If not, the device sends the packet to the upper layer protocol for processing.1.2 Configuring UDP HelperFollow these steps to configure UDP Helper:To do… Use the command… RemarksEnter system view system-view —Enable UDP Helper udp-helper enable RequiredDisabled by default.Enable the forwarding ofpackets with the specifiedUDP destination portnumber(s)udp-helper port{ port-number | dns |netbios-ds | netbios-ns |tacacs | tftp | time }RequiredBy default, no UDP portnumber is specified.Enter VLAN interface view interface Vlan-interfacevlan-id —
