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- Table of Contents
-
- 02-IP Services Volume
- 00-IP Services Volume Organization
- 01-IP Addressing Configuration
- 02-ARP Configuration.doc
- 03-DHCP Configuration.doc
- 04-DNS Configuration
- 05-IP Performance Configuration
- 06-UDP Helper Configuration
- 07-URPF Configuration
- 08-IPv6 Basics Configuration
- 09-Dual Stack Configuration
- 10-Tunneling Configuration
- 11-sFlow Configuration
- Related Documents
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| Title | Size | Download |
|---|---|---|
| 06-UDP Helper Configuration | 57.95 KB |
When configuring UDP Helper, go to these sections for information you are interested in:
l Displaying and Maintaining UDP Helper
l UDP Helper Configuration Examples
UDP Helper can be currently configured on VLAN interfaces only.
Introduction to UDP Helper
Sometimes, a host needs to forward broadcasts to obtain network configuration information or request the names of other devices on the network. However, if the server or the device to be requested is located in another broadcast domain, the host cannot obtain such information through broadcast.
To solve this problem, the device provides the UDP Helper function to relay specified UDP packets. In other words, UDP Helper functions as a relay agent that converts UDP broadcast packets into unicast packets and forwards them to a specified destination server.
With UDP Helper enabled, the device decides whether to forward a received UDP broadcast packet according to the UDP destination port number of the packet.
l 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.
l If not, the device sends the packet to the upper layer protocol for processing.
Configuring UDP Helper
Follow these steps to configure UDP Helper:
|
To do… |
Use the command… |
Remarks |
|
Enter system view |
system-view |
— |
|
Enable UDP Helper |
udp-helper enable |
Required Disabled by default. |
|
Enable the forwarding of packets with the specified UDP destination port number(s) |
udp-helper port { port-number | dns | netbios-ds | netbios-ns | tacacs | tftp | time } |
Required No UDP port number is specified by default. |
|
Enter interface view |
interface interface-type interface-number |
— |
|
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. |
l 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.
l 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.
l The configuration of all UDP ports is removed if you disable UDP Helper.
l You can configure up to 256 UDP port numbers to enable the forwarding of packets with these UDP port numbers.
l You can configure up to 20 destination servers on an interface.
Displaying and Maintaining UDP Helper
|
To do… |
Use the command… |
Remarks |
|
Displays the information of forwarded UDP packets |
display udp-helper server [ interface interface-type interface-number ] |
Available in any view |
|
Clear statistics about packets forwarded |
reset udp-helper packet |
Available in user view |
UDP Helper Configuration Examples
Network requirements
On Switch A, configure UDP helper to forward broadcast packets (with UDP destination port number 55 and destination IP address 255.255.255.255 or 10.110.255.255 to the destination server 10.2.1.1/16.
Network diagram
Figure 1-1 Network diagram for UDP Helper configuration
Configuration procedure
The following configuration assumes that a route from Switch A to the network segment 10.2.0.0/16 is available.
# Enable UDP Helper.
<SwitchA> system-view
[SwitchA] udp-helper enable
# Enable the forwarding broadcast packets with the UDP destination port 55.
[SwitchA] udp-helper port 55
# Specify the destination server 10.2.1.1 on VLAN-interface 1.
[SwitchA] interface vlan-interface 1
[SwitchA-Vlan-interface1] ip address 10.110.1.1 16
[SwitchA-Vlan-interface1] udp-helper server 10.2.1.1
