Configuring Udp Helper; Overview; Configuration Restrictions And Guidelines; Configuration Procedure - HP 6125G Configuration Manual

Configuring UDP helper

Overview

UDP helper functions as a relay agent that converts UDP broadcast packets into unicast packets and
forwards them to a specified destination server. This is helpful when a host cannot obtain network
configuration information or request device names through broadcasting because the server or host to be
requested is located on another broadcast domain.
With UDP helper enabled, a device decides whether to forward a received UDP broadcast packet
according to the UDP destination port number of the packet.
• If the destination port number of the packet matches the one pre-configured on the device, the
device modifies the destination IP address in the IP header, and then sends the packet to the
specified destination server.
If the destination port number of the packet does not match the one pre-configured on the device,
•
the device sends the packet to the upper layer protocol for processing.

Configuration restrictions and guidelines

• The receiving of directed broadcasts to a directly connected network is disabled by default on the
switch. As a result, UDP helper is available only when the ip forward-broadcast command is
configured in system view. For more information about reception and forwarding of directed
broadcasts to a directly connected network, see
A UDP helper enabled device must not forward DHCP broadcast packets that use destination port
•
67 or 68. Therefore, the UDP port numbers set with the udp-helper port command must not include
67 or 68.
You can specify a port number or the corresponding parameter for a UDP port to forward packets.
•
For example, udp-helper port 53 and udp-helper port dns specify the same UDP port number.
The configuration of all UDP ports is removed if you disable UDP helper.
•
You can configure up to 256 UDP port numbers to enable the forwarding of packets with these UDP
•
port numbers.
• You can configure up to 20 destination servers on an interface.

Configuration procedure

To configure UDP helper:
Step
1. Enter system view.
Enable UDP helper.
2.
3. Enable the forwarding of
packets with the specified
UDP destination port
number(s).
"Configuring IP performance
Command
system-view
udp-helper enable
udp-helper port { port-number | dns |
netbios-ds | netbios-ns | tacacs | tftp
| time }
76
optimization."
Remarks
N/A
Disabled by default.
No UDP port number is specified
by default.