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- Table of Contents
-
- 05-Layer 3 - IP Services Configuration Guide
- 00-Preface
- 01-ARP configuration
- 02-IP addressing configuration
- 03-DHCP configuration
- 04-DNS configuration
- 05-IP forwarding basics configuration
- 06-Adjacency table configuration
- 07-IP performance optimization configuration
- 08-UDP Helper configuration
- 09-IPv6 basics configuration
- 10-DHCPv6 configuration
- 11-Tunneling configuration
- 12-GRE configuration
- 13-IRDP configuration
- Related Documents
-
| Title | Size | Download |
|---|---|---|
| 08-UDP Helper configuration | 83.55 KB |
Overview
UDP helper enables a device to convert received UDP broadcast packets into unicast packets and forward them to a specific server. UDP helper is suitable for the scenario where hosts cannot obtain configuration information or device names by broadcasting packets because the target server or host resides on another broadcast domain.
Upon receiving a UDP broadcast packet (the destination address is 255.255.255.255 or a directed broadcast address destined for the network directly connected to the receiving interface), UDP helper uses the configured UDP ports to match the UDP destination port number of the packet.
· If a match is found, UDP helper modifies the destination IP address of the packet and sends the packet to the specified destination server.
· If no match is found, UDP helper sends the packet to the upper layer protocol.
Configuration guidelines
When you configure UDP helper, follow these guidelines:
· Do not set UDP ports 67 and 68 for UDP helper, because UDP helper cannot forward DHCP broadcast packets.
· You can specify up to 256 UDP ports for UDP helper.
· Specify destination servers on the interface that receives broadcast packets. You can specify up to 20 destination servers on an interface.
Configuration procedure
|
Step |
Command |
Remarks |
|
1. Enter system view. |
system-view |
N/A |
|
2. Enable UDP helper. |
udp-helper enable |
By default, UDP helper is disabled. |
|
3. Specify a UDP port. |
udp-helper port { port-number | dns | netbios-ds | netbios-ns | tacacs | tftp | time } |
By default, no UDP port is specified. |
|
4. Enter interface view. |
interface interface-type interface-number |
N/A |
|
5. Specify a destination server. |
udp-helper server ip-address |
By default, no destination server is specified. |
Displaying and maintaining UDP helper
Execute display command in any view and reset command in user view.
|
Task |
Command |
|
Display information about packets forwarded by UDP helper. |
display udp-helper interface interface-type interface-number |
|
Clear UDP helper statistics. |
reset udp-helper statistics |
UDP helper configuration example
By default, Ethernet, VLAN, and aggregate interfaces are shut down. You must use the undo shutdown command to bring them up. This example assumes that all these interfaces are already up.
Network requirements
As shown in Figure 1, 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.
Configuration procedure
Make sure Switch A can reach the subnet 10.2.0.0/16.
# Enable UDP helper.
[SwitchA] System-view
[SwitchA] udp-helper enable
# Enable UDP helper to forward 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
Verifying the configuration
# Display information about packets forwarded by UDP helper on VLAN-interface 1.
[SwitchA-Vlan-interface1] display udp-helper interface vlan-interface 1
Interface Server address Packets sent
Vlan-interface1 10.2.1.1 5
