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- Table of Contents
-
- 03-Layer 3 Configuration Guide
- 00-Preface
- 01-ARP Configuration
- 02-IP Addressing Configuration
- 03-DHCP Configuration
- 04-DNS Configuration
- 05-IP Performance Optimization Configuration
- 06-UDP Helper Configuration
- 07-IPv6 Basics Configuration
- 08-IP Routing Basics Configuration
- 09-Static Routing Configuration
- 10-IPv6 Static Routing Configuration
- 11-RIP Configuration
- 12-RIPng Configuration
- Related Documents
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| Title | Size | Download |
|---|---|---|
| 06-UDP Helper Configuration | 74.35 KB |
This chapter includes these sections:
· Displaying and maintaining UDP helper
· UDP helper configuration example
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NOTE: · The term "switch" or "device" in this chapter refers to the switching engine on a WX3000E wireless switch. · The WX3000E series comprises WX3024E and WX3010E wireless switches. · The port numbers in this chapter are for illustration only. · UDP helper can be configured on VLAN interfaces only. |
Introduction to UDP helper
UDP helper functions as a relay agent that converts UDP broadcast packets into unicast packets and forwards them to a specified destination server. This is helpful when a host cannot obtain network configuration information or request device names through broadcasting because the server or host to be requested is located on another broadcast domain.
With UDP helper enabled, a device decides whether to forward a received UDP broadcast packet according to the UDP destination port number of the packet.
· 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.
· 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 |
— |
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Enable UDP helper |
udp-helper enable |
Required Disabled by default. |
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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 |
— |
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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. |
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CAUTION: · On the devices supporting the directed broadcast suppression function, the receiving of directed broadcasts to a directly connected network is disabled by default. As a result, UDP helper is available only when the ip forward-broadcast command is configured in system view. For more information about reception and forwarding of directed broadcasts to a directly connected network, see the chapter “IP performance optimization configuration.” · The UDP helper enabled device 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 a port number or the corresponding parameter for an UDP port to forward packets. 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 256 UDP port numbers to enable the forwarding of packets with these UDP port numbers. · You can configure up to 20 destination servers on an interface. |
Displaying and maintaining UDP helper
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To do… |
Use the command… |
Remarks |
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Displays the information of forwarded UDP packets |
display udp-helper server [ interface interface-type interface-number ] [ | { begin | exclude | include } regular-expression ] |
Available in any view |
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Clear statistics about packets forwarded |
reset udp-helper packet |
Available in user view |
UDP helper configuration example
Network requirements
As shown in Figure 1, the IP address of VLAN-interface 1 of Switch A is 10.110.1.1/16, and the interface connects to the subnet 10.110.0.0/16.
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.
Figure 1 Network diagram for UDP helper configuration
Configuration procedure
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NOTE: Make sure that a route from Switch A to the subnet 10.2.0.0/16 is available. |
# Enable Switch A to receive directed broadcasts.
<SwitchA> system-view
[SwitchA] ip forward-broadcast
# Enable UDP helper.
[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
