928 CHAPTER 74: UDP HELPER CONFIGURATION
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CAUTION:
■ 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.
■ For the dns, netbios-ds, netbios-ns, tacacs, tftp, and time keywords, you
can specify port numbers or the corresponding parameters. 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 20 destination servers on a VLAN interface.
Displaying and
Maintaining UDP
Helper
UDP Helper
Configuration
Example
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.
Network diagram
Figure 271 Network diagram for UDP Helper configuration
Configuration procedure
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The following configuration assumes that a route from Switch A to the network
segment 10.2.0.0/16 is available.
Specify the destination server
to which UDP packets are to
be forwarded
udp-helper server ip-address Required
No destination server is
specified by default.
To do… Use the command… Remarks
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
IP network
Vlan-int1
10.110.1.1/16
Vlan-int1
10.2.1.1/16
Switch A Switch B
Server
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