Configuring Udp Helper; Overview; Configuration Guidelines; Configuration Procedure - H3C MSR 2600 Configuration Manual

Configuring UDP helper

Overview

UDP helper enables a device to convert received UDP broadcast packets into unicast packets and
forward them to a specific server. UDP helper is suitable for the scenario where hosts cannot obtain
configuration information or device names by broadcasting packets because the target server or host
resides on another broadcast domain.
Upon receiving a UDP broadcast packet (the destination address is 255.255.255.255 or a directed
broadcast address destined for the network directly connected to the receiving interface), UDP helper
matches the UDP destination port number of the packet against the configured UDP ports.
If a match is found, UDP helper modifies the destination IP address of the packet and sends the
•
packet to the specified destination server.
• If no match is found, UDP helper sends the packet to the upper layer protocol.

Configuration guidelines

Follow these guidelines when you configure UDP helper:
By default, an interface does not receive directed broadcasts destined for the directly connected
•
network. To use UDP helper, execute the ip forward-broadcast command in interface view. For
more information about receiving directed broadcasts destined for the directly connected network,
see "Optimizing IP performance."
Do not set UDP ports 67 and 68 for UDP helper because UDP helper cannot forward DHCP
•
broadcast packets.
You can specify up to 256 UDP ports for UDP helper.
•
• Specify destination servers on the interface that receives broadcast packets. You can specify up to
20 destination servers on an interface.

Configuration procedure

Step
1. Enter system view.
2. Enable UDP helper.
3. Specify a UDP port.
4. Enter interface view.
5. Specify a destination
server.
Command
system-view
udp-helper enable
udp-helper port { port-number | dns |
netbios-ds | netbios-ns | tacacs | tftp |
time }
interface interface-type interface-number
udp-helper server ip-address
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Remarks
N/A
By default, UDP helper is
disabled.
By default, no UDP port is
specified.
N/A
By default, no destination server
is specified.