1-2By default, with UDP Helper enabled, the device forwards broadcast packets with the six UDPdestination port numbers listed in Table 1-1.Table 1-1 List of default UDP portsProtocol UDP port numberDNS (Domain Name System) 53NetBIOS-DS (NetBIOS Datagram Service) 138NetBIOS-NS (NetBIOS Name Service) 137TACACS (Terminal Access Controller Access ControlSystem) 49TFTP (Trivial File Transfer Protocol) 69Time Service 37Configuring 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.Specify a UDP port numberudp-helper port { port-number |dns | netbios-ds | netbios-ns |tacacs | tftp | time }OptionalBy default, the device enabled withUDP Helper forwards thebroadcast packets containing anyof the six port numbers 53, 138,137, 49, 69 and 37.Enable the UDP Helper TTL-keepfunction udp-helper ttl-keep enableOptionalDisabled by default. That is, UDPHelper does not forward IPbroadcasts with the TTL field being1.Enter VLAN interface view interface Vlan-interface vlan-id —Specify the destination server towhich the UDP packets are to beforwardedudp-helper server ip-addressRequiredNo destination server is specifiedby default.
