HP 6125XLG R2306-HP 6125XLG Blade Switch Layer 3 - IP Services Configuration G - Page 122

Configuring UDP helper, Overview, Configuration guidelines, Configuration procedure

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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: • On some devices, an interface does not receive directed broadcasts destined for the directly connected network by default. To use UDP helper on such devices, execute the ip forward-broadcast command in interface view. On some other devices, an interface can receive directed broadcasts destined for the directly connected network by default, and you do not need to execute the ip forward-broadcast command. For more information about receiving directed broadcasts destined for the directly connected network, see "Optimizing IP performance." • UDP helper 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 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. Command system-view udp-helper enable udp-helper port { port-number | dns | netbios-ds | netbios-ns | tacacs | tftp | time } interface interface-type interface-number Remarks N/A By default, UDP helper is disabled. By default, no UDP port is specified. N/A 114

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114
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:
•
On some devices, an interface does not receive directed broadcasts destined for the directly
connected network by default. To use UDP helper on such devices, execute the
ip
forward-broadcast
command in interface view. On some other devices, an interface can receive
directed broadcasts destined for the directly connected network by default, and you do not need to
execute the
ip forward-broadcast
command. For more information about receiving directed
broadcasts destined for the directly connected network, see "
Optimizing IP performance
."
•
UDP helper 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 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
Command
Remarks
1.
Enter system view.
system-view
N/A
2.
Enable UDP helper.
udp-helper enable
By default, UDP helper is
disabled.
3.
Specify a UDP port.
udp-helper port
{
port-number
|
dns
|
netbios
-
ds
|
netbios-ns
|
tacacs
|
tftp
|
time
}
By default, no UDP port is
specified.
4.
Enter interface view.
interface
interface-type interface-number
N/A