Configuring UDP helper 1

Overview·· 1

Configuration restrictions and guidelines 1

Configuring UDP helper to convert broadcast to unicast 1

Configuring UDP helper to convert broadcast to multicast 2

Displaying and maintaining UDP helper 3

UDP helper configuration examples 3

Configuring UDP helper to convert broadcast to unicast 3

Configuring UDP helper to convert broadcast to multicast 4

Overview

UDP helper can provide the following packet conversion for packets with specific UDP destination port numbers:

·     Convert broadcast to unicast, and forward the unicast packets to specific destinations.

·     Convert broadcast to multicast, and forward the multicast packets.

 

NOTE: The term "interface" in this chapter collectively refers to VLAN interfaces, Layer 3 Ethernet interfaces and subinterfaces, and Layer 3 aggregate interfaces and subinterfaces. You can set an Ethernet port as a Layer 3 interface by using the port link-mode route command (see Layer 2—LAN Switching Configuration Guide).

 

Configuration restrictions and guidelines

When you configure UDP helper, follow these restrictions and guidelines:

·     By default, an interface on the device does not receive directed broadcasts destined for the directly connected network. To use UDP helper, execute the ip forward-broadcast command. For more information about receiving directed broadcasts destined for the directly connected network, see "Optimizing IP performance."

·     Do not set UDP ports 67 and 68 for UDP helper, because UDP helper cannot forward DHCP broadcast packets.

·     You can specify a maximum of 256 UDP ports for UDP helper.

·     You can specify a maximum of 20 unicast and multicast addresses for UDP helper to convert broadcast packets on an interface.

Configuring UDP helper to convert broadcast to unicast

You can configure UDP helper to convert broadcast packets with specific UDP port numbers to unicast packets.

Upon receiving a UDP broadcast packet, UDP helper uses the configured UDP ports to match the UDP destination port number of the packet.

·     If a match is found, UDP helper duplicates the packet and modifies the destination IP address of the copy to the configured unicast address. Then UDP helper forwards the unicast packet to the unicast address.

·     If no match is found, UDP helper does not process the packet.

To configure UDP helper to convert broadcast to unicast:

 

Step	Command	Remarks
1.     Enter system view.	system-view	N/A
1.     Enable UDP helper.	udp-helper enable	By default, UDP helper is disabled.
2.     Specify a UDP port.	udp-helper port { port-number | dns | netbios-ds | netbios-ns | tacacs | tftp | time }	By default, no UDP port is specified.
3.     Enter interface view.	interface interface-type interface-number	N/A
4.     Specify a destination server for UDP helper to convert broadcast to unicast.	udp-helper server ip-address [ global | vpn-instance vpn-instance-name ]	By default, no destination server is specified. If you specify multiple destination servers, UDP helper creates one copy for each server. Use this command on the interface that receives broadcast packets.

 

Configuring UDP helper to convert broadcast to multicast

You can configure UDP helper to convert broadcast packets with specific UDP port numbers to multicast packets.

Upon receiving a UDP broadcast packet, UDP helper uses the configured UDP ports to match the UDP destination port number of the packet.

·     If a match is found, UDP helper duplicates the packet and modifies the destination IP address of the copy to the configured multicast address. Then UDP helper forwards the packet to the multicast group.

·     If no match is found, UDP helper does not process the packet.

To configure UDP helper to convert broadcast to multicast:

 

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 multicast address for UDP helper to convert broadcast to multicast.	udp-helper broadcast-map multicast-address [ acl acl-number ]	By default, no destination multicast address is specified for UDP helper. If you specify multiple multicast addresses, UDP helper creates one copy for each address. Use this command on the interface that receives broadcast packets.

 

Displaying and maintaining UDP helper

Execute display command in any view and reset command in user view.

 

Task	Command
Display information about broadcast to unicast conversion by UDP helper on an interface.	display udp-helper interface interface-type interface-number
Clear packet statistics for UDP helper.	reset udp-helper statistics

 

UDP helper configuration examples

Configuring UDP helper to convert broadcast to unicast

Network requirements

As shown in Figure 1, configure UDP helper to convert broadcast to unicast on VLAN-interface 1 of Switch A. This feature enables Switch A to forward broadcast packets with UDP destination port number 55 to the destination server 10.2.1.1/16.

Figure 1 Network diagram

 

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 vpn-instance a

Verifying the configuration

# Display information about broadcast to unicast conversion by UDP helper on VLAN-interface 1.

[SwitchA-Vlan-interface1] display udp-helper interface vlan-interface 1

Interface                Server VPN instance           Server address Packets sent

Vlan-interface1          N/A                           10.2.1.1       5

Configuring UDP helper to convert broadcast to multicast

Network requirements

As shown in Figure 2, VLAN-interface 1 of Switch B can receive multicast packets destined to 225.1.1.1.

Configure UDP helper to convert broadcast to multicast on VLAN-interface 1 of Switch A. This feature enables Switch A to forward broadcast packets with UDP destination port number 55 to the multicast group 225.1.1.1.

Figure 2 Network diagram

 

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

# Configure UDP helper to convert broadcast packets to multicast packets destined for 225.1.1.1.

[SwitchA] interface vlan-interface 1

[SwitchA-Vlan-interface1] ip address 10.110.1.1 16

[SwitchA-Vlan-interface1] udp-helper broadcast-map 225.1.1.1

[SwitchA-Vlan-interface1] quit

# Enable IP multicast routing globally.

[SwitchA] multicast routing

[SwitchA-mrib] quit

Enable PIM-DIM and IGMP on VLAN-interface 1.

[SwitchA] interface vlan-interface 1

[SwitchA-Vlan-interface1] pim dm

[SwitchA-Vlan-interface1] igmp enable

# Configure VLAN-interface 1 as a static member of the multicast group 225.1.1.1.

[SwitchA-Vlan-interface1] igmp static-group 225.1.1.1

[SwitchA-Vlan-interface1] quit

# Enable PIM-DIM and IGMP on VLAN-interface 2.

[SwitchA] interface vlan-interface 2

[SwitchA-Vlan-interface2] pim dm

[SwitchA-Vlan-interface2] igmp enable

# Configure VLAN-interface 2 as a static member of the multicast group 225.1.1.1.

[SwitchA-Vlan-interface2] igmp static-group 225.1.1.1

Verifying the configuration

Verify that you can capture multicast packets from Switch A on Switch B.