Login
- Table of Contents
-
- H3C S3610[S5510] Series Ethernet Switches Operation Manual-Release 5303(V1.01)
- 00-1Cover
- 00-2Product Overview
- 01-Login Configuration
- 02-VLAN Configuration
- 03-IP Addressing and Performance Configuration
- 04-QinQ-BPDU Tunneling Configuration
- 05-Port Correlation Configuration
- 06-Link Aggregation Configuration
- 07-MAC Address Table Management Configuration
- 08-IP Source Guard Configuration
- 09-MSTP Configuration
- 10-IPv6 Configuration
- 11-Routing Overview
- 12-IPv4 Routing Configuration
- 13-BFD-GR Configuration
- 14-IPv6 Routing Configuration
- 15-Multicast Protocol Configuration
- 16-802.1x-HABP-MAC Authentication Configuration
- 17-AAA-RADIUS-HWTACACS Configuration
- 18-ARP Configuration
- 19-DHCP Configuration
- 20-ACL Configuration
- 21-QoS Configuration
- 22-Port Mirroring Configuration
- 23-Cluster Management Configuration
- 24-UDP Helper Configuration
- 25-SNMP-RMON Configuration
- 26-NTP Configuration
- 27-DNS Configuration
- 28-File System Management Configuration
- 29-Information Center Configuration
- 30-System Maintaining and Debugging Configuration
- 31-NQA Configuration
- 32-VRRP Configuration
- 33-SSH Configuration
- 34-MCE Configuration
- 35-OAM Configuration
- 36-DLDP Configuration
- 37-RRPP Configuration
- 38-SSL-HTTPS Configuration
- 39-PKI Configuration
- 40-Appendix
- Related Documents
-
| Title | Size | Download |
|---|---|---|
| 24-UDP Helper Configuration | 44.73 KB |
Table of Contents
Chapter 1 UDP Helper Configuration
1.1 Introduction to UDP Helper
1.3 Displaying and Maintaining UDP Helper
1.4 UDP Helper Configuration Example
Chapter 1 UDP Helper Configuration
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
1.1 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.
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 |
|
Trivial File Transfer Protocol (TFTP) |
69 |
|
Domain Name System (DNS) |
53 |
|
Time service |
37 |
|
NetBIOS name service (NetBIOS-NS) |
137 |
|
NetBIOS datagram service (NetBIOS-DS) |
138 |
|
Terminal access controller access control system (TACACS) |
49 |
1.2 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 } |
Optional By default, the UDP helper enabled device forwards broadcast packets with any of the destination port numbers 69, 53, 37, 137, 138, and 49. |
|
Enter VLAN interface view |
interface Vlan-interface vlan-id |
— |
|
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. |
Caution:
l 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.
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 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.
l 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.
l The configuration of all UDP ports (including the default ports) is removed if you disable UDP Helper.
l 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.
II. Network diagram
Figure 1-1 Network diagram for UDP Helper configuration
III. Configuration procedure
& Note:
The following configuration assumes that a route from Switch A to the network segment 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 number 55.
[SwitchA] udp-helper port 55
# Specify the server with the IP address of 10.2.1.1 as the destination server to which UDP packets are to be forwarded.
[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
