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- Table of Contents
-
- H3C WX3000 Series Unified Switches Switching Engine Configuration Guide-6W103
- 00-Preface
- 01-CLI Configuration
- 02-Login Configuration
- 03-Configuration File Management Configuration
- 04-VLAN Configuration
- 05-Auto Detect Configuration
- 06-Voice VLAN Configuration
- 07-GVRP Configuration
- 08-Basic Port Configuration
- 09-Link Aggregation Configuration
- 10-Port Isolation Configuration
- 11-Port Security-Port Binding Configuration
- 12-DLDP Configuration
- 13-MAC Address Table Management Configuration
- 14-MSTP Configuration
- 15-802.1x and System Guard Configuration
- 16-AAA Configuration
- 17-MAC Address Authentication Configuration
- 18-IP Address and Performance Configuration
- 19-DHCP Configuration
- 20-ACL Configuration
- 21-QoS-QoS Profile Configuration
- 22-Mirroring Configuration
- 23-ARP Configuration
- 24-SNMP-RMON Configuration
- 25-Multicast Configuration
- 26-NTP Configuration
- 27-SSH Configuration
- 28-File System Management Configuration
- 29-FTP-SFTP-TFTP Configuration
- 30-Information Center Configuration
- 31-System Maintenance and Debugging Configuration
- 32-VLAN-VPN Configuration
- 33-HWPing Configuration
- 34-DNS Configuration
- 35-Smart Link-Monitor Link Configuration
- 36-PoE-PoE Profile Configuration
- 37-Routing Protocol Configuration
- 38-UDP Helper Configuration
- 39-Acronyms
- 40-Index
- Related Documents
-
| Title | Size | Download |
|---|---|---|
| 38-UDP Helper Configuration | 50.73 KB |
Table of Contents
Displaying and Maintaining UDP Helper
UDP Helper Configuration Example
Cross-Network Computer Search Through UDP Helper
When configuring UDP helper, go to these sections for information you are interested in:
l Displaying and Maintaining UDP Helper
l UDP Helper Configuration Example
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 unified switches provide 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 Otherwise, the device sends the packet to the upper layer protocol for processing.
Relay forwarding of BOOTP/DHCP broadcast packets is implemented by the DHCP relay function using UDP ports 67 and 68, so these two ports cannot be configured as UDP Helper relay ports.
By default, with UDP Helper enabled, the device forwards broadcast packets with the six UDP destination port numbers listed in Table 1-1.
Table 1-1 List of default UDP ports
|
Protocol |
UDP port number |
|
DNS (Domain Name System) |
53 |
|
NetBIOS-DS (NetBIOS Datagram Service) |
138 |
|
NetBIOS-NS (NetBIOS Name Service) |
137 |
|
TACACS (Terminal Access Controller Access Control System) |
49 |
|
TFTP (Trivial File Transfer Protocol) |
69 |
|
Time Service |
37 |
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. |
|
Specify a UDP port number |
udp-helper port { port-number | dns | netbios-ds | netbios-ns | tacacs | tftp | time } |
Optional By default, the device enabled with UDP Helper forwards the broadcast packets containing any of the six port numbers 53, 138, 137, 49, 69 and 37. |
|
Enter VLAN interface view |
interface Vlan-interface vlan-id |
— |
|
Specify the destination server to which the UDP packets are to be forwarded |
udp-helper server ip-address |
Required No destination server is specified by default. |
l You need to enable UDP Helper before specifying any UDP port to match UDP broadcasts; otherwise, the configuration fails. When the UDP helper function is disabled, all configured UDP ports are disabled, including the default ports.
l The dns, netbios-ds, netbios-ns, tacacs, tftp, and time keywords correspond to the six default ports. You can configure the default ports by specifying port numbers or the corresponding parameters. For example, udp-helper port 53 and udp-helper port dns specify the same port.
l You can specify up to 20 destination server addresses on a VLAN interface.
l If UDP Helper is enabled after a destination server is configured for a VLAN interface, the broadcasts from interfaces belonging to the VLAN and having a matching UDP port will be unicast to the destination server.
Displaying and Maintaining UDP Helper
|
To do… |
Use the command… |
Remarks |
|
Display the UDP broadcast relay forwarding information of a specified VLAN interface on the device |
display udp-helper server [ interface vlan-interface vlan-id ] |
Available in any view |
|
Clear statistics about packets forwarded by UDP Helper |
reset udp-helper packet |
Available in user view |
UDP Helper Configuration Example
Cross-Network Computer Search Through UDP Helper
Network requirements
As shown in Figure 1-1, PC A resides on network segment 192.168.1.0/24 and PC B on 192.168.10.0/24; they are connected through Switch A and are routable to each other. It is required to configure UDP Helper on Switch A, so that PC A can find PC B through computer search. (Broadcasts with UDP port 137 are used for searching.)
Figure 1-1 Network diagram for UDP Helper configuration
Configuration procedure
# Enable UDP Helper on Switch A.
<SwitchA> system-view
[SwitchA] udp-helper enable
# Configure Switch A to forward broadcasts containing the destination UDP port number 137. (By default, the device enabled with UDP Helper forwards the broadcasts containing the destination UDP port number 137.)
[SwitchA] udp-helper port 137
# Specify the destination server IP address on Vlan-interface 1.
[SwitchA] interface vlan-interface 1
[SwitchA-Vlan-interface1] udp-helper server 192.168.10.2
