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Configuration Guide - IP Service

CloudEngine 12800 and 12800E V200R005C00

This document describes the configurations of IP Service, including IP address, ARP, DHCP, DNS, IP performance optimization, IPv6, DHCPv6, and IPv6 DNS.

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Configuring UDP Helper

Configuring UDP Helper

The UDP helper function relays the UDP broadcast packets destined for specified ports.

Pre-configuration Tasks

Before configuring UDP helper, complete the following task:

  • Configuring a reachable route from the switch to the destination server


  1. Run system-view

    The system view is displayed.

  2. Run ip udp-helper enable

    UDP helper is enabled.

    By default, UDP Helper is disabled.

    • After UDP Helper is enabled, the device can relay broadcast packets carrying one of the following six default UDP port numbers: 37 (Time), 49 (TACACS), 53 (DNS), 69 (TFTP), 137 (NetBIOS-NS), and 138 (NetBIOS-DS).
    • UDP Helper cannot relay DHCP packets. Specifically, the UDP port number cannot be set to 67 or 68. DHCP relay must be enabled to relay DHCP packets.
    • If the interface number to be configured is not one of the default UDP port numbers, go to Step 3 to configure the UDP port number.
    • If the device does not need to relay broadcast packets carrying one of the following UDP interface numbers: 37 (Time), 49 (TACACS), 53 (DNS), 69 (TFTP), 137 (NetBIOS-NS), and 138 (NetBIOS-DS), go to Step 4.

  3. (Optional) Run ip udp-helper port port-number [ description description ]

    The UDP destination port to which UDP broadcast packets are relayed is specified.

  4. (Optional) Run ip udp-helper port disable { port-number | dns | netbios-ds | netbios-ns | tacacs | tftp | time }

    The UDP destination port to which UDP broadcast packets are relayed is deleted.

  5. Run interface interface-type interface-number

    The interface view is displayed.

    The interface must be a VLANIF interface.

  6. Run ip udp-helper server ip-address

    The destination server for UDP helper is specified.

  7. Run commit

    The configuration is committed.

Verifying the Configuration

  • Run the display ip udp-helper port command to check the UDP port numbers of the packets that need to be relayed.
Updated: 2019-04-18

Document ID: EDOC1100039535

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