
Operation Manual – UDP Helper
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 UDP Helper Configuration
1-3
Caution:
z
By default, S3610&S5510 series Ethernet switches do not receiving directed
broadcasts. To ensure that UDP Helper is available, you must use the
ip
forward-broadcast
command in system view first. If NTP broadcast mode or
DHCP is configured on the switches, the switches will automatically receiving
directed broadcasts. In this case, UDP Helper can take effect even though you do
not configure the
ip forward-broadcast
command. For details about the
ip
forward-broadcast
command, see the “IP Address and Performance” part of this
manual.
z
The UDP Helper enabled device cannot forward DHCP broadcast packets. That is
to say, the UDP port number cannot be set to 67 or 68.
z
The
dns
,
netbios-ds
,
netbios-ns
,
tacacs
,
tftp
, and
time
keywords correspond to
the six default UDP port numbers. You can configure these default UDP port
numbers by specifying port numbers or the corresponding parameters. For example,
udp-helper port
53 and
udp-helper port
dns
specify the same UDP port number.
z
When you view the configuration information by using the
display
current-configuration
command, the UDP Helper configuration of the default ports
will not be displayed. UDP Helper configuration of these ports will be displayed only
after UDP Helper is disabled.
z
The configuration of all UDP ports (including the default ports) is removed if you
disable UDP Helper.
z
You can configure up to 20 destination servers on a VLAN interface.
1.3 Displaying and Maintaining UDP Helper
To do…
Use the command…
Remarks
Displays the information
of forwarded UDP packets
display udp-helper
server
[
interface
Vlan-interface vlan-id
]
Available in any view
Clear statistics about
packets forwarded
reset udp-helper packet
Available in user view
1.4 UDP Helper Configuration Example
I. Network requirements
The interface VLAN-interface 1 of Switch A has the IP address of 10.110.1.1/16,
connecting to the network segment 10.110.0.0/16. Enable the forwarding of broadcast
packets with the UDP destination port number 55 to the destination server 10.2.1.1/16.