udp-helper port

Function

The udp-helper port command specifies the UDP ports to which UDP broadcast packets are relayed.

The undo udp-helper port command deletes the UDP ports to which packets are relayed.

By default, no UDP port is specified. After UDP helper is enabled, the switch relays broadcast packets destined for ports 37, 49, 53, 69, 137, and 138 by default.

Format

udp-helper port { port-number | dns | netbios-ds | netbios-ns | tacacs | tftp | time }

undo udp-helper port { port-number | dns | netbios-ds | netbios-ns | tacacs | tftp | time }

Parameters

Parameter	Description	Value
port-number	Specifies the UDP ports to which packets are relayed.	The value is an integer that ranges from 1 to 65535, excluding 68.
dns	Relays the UDP broadcast packets sent by DNS. The UDP port number is 53.	-
netbios-ds	Relays the UDP broadcast packets sent by NetBIOS-DS. The UDP port number is 138.	-
netbios-ns	Relays the UDP broadcast packets sent by NetBIOS-NS. The UDP port number is 137.	-
tacacs	Relays the UDP broadcast packets sent by TACACS. The UDP port number is 49.	-
tftp	Relays the UDP broadcast packets sent by TFTP. The UDP port number is 69.	-
time	Relays the UDP broadcast packets sent by time service. The UDP port number is 37.	-

Views

System view

Default Level

2: Configuration level

Usage Guidelines

Usage Scenario

After UDP helper is enabled and the UDP ports are specified, the switch relays the received UDP broadcast packets destined for the specified ports.

Precautions

The udp-helper port command takes effect globally. That is, if the switch is configured to relay packets destined for a UDP port, all the interfaces configured with the destination server address will relay such packets.

UDP helper enables a device to relay DHCP packets destined for UDP port 67 (that is, DHCP packets sent to the DHCP server).

However, a UDP helper-enabled device cannot relay DHCP packets destined for UDP port 68 (that is, DHCP packets sent to the DHCP client). To relay this type of DHCP packets, you must enable the DHCP relay function.

The switch supports a maximum of 16 UDP ports.

Example

# Configure the switch to relay the broadcast packets destined for UDP port 100.

<HUAWEI> system-view
[HUAWEI] udp-helper enable
[HUAWEI] udp-helper port 100