01-S12500_UDP_Helper_Configuration_Examples
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This document provides UDP helper configuration examples.
UDP helper enables a device to convert received UDP broadcast packets with a specific UDP destination port number into unicast packets and forward them to a specific server on another broadcast domain.
The configuration examples in this document were created and verified in a lab environment, and all the devices were started with the factory default configuration. When you are working on a live network, make sure you understand the potential impact of every command on your network.
This document assumes that you have basic knowledge of H3C UDP helper.
As shown in Figure 1, configure UDP helper on Switch A to forward broadcast packets with UDP destination port number 53 from Host A and Host B to the destination DNS server at 192.168.2.2.
To convert the broadcast packets from Host A and Host B into unicast packets and forward them to the DNS server, specify the IP address of the DNS server for UDP helper on VLAN-interface 3.
This configuration example was created and verified on S12500-CMW710-R7129.
When you configure UDP helper, follow these restrictions and guidelines:
· UDP ports 67 and 68 are used by DHCP. Do not set UDP ports 67 and 68 for UDP helper because UDP helper cannot forward DHCP broadcast packets.
· Disabling UDP helper removes all UDP ports configured for UDP helper.
· You can configure up to 20 destination servers on an interface.
· 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.
# Create VLAN 2 and VLAN 3, and configure the IP addresses of VLAN interfaces. (Details not shown.)
# Enable UDP helper.
<SwitchA> system-view
[SwitchA] udp-helper enable
# Enable forwarding broadcast packets with the UDP destination port 53.
[SwitchA] udp-helper port 53
# Specify the destination DNS server 192.168.2.2 on VLAN-interface 3.
[SwitchA] interface Vlan-interface 3
[SwitchA-Vlan-interface3] udp-helper server 192.168.2.2
[SwitchA-Vlan-interface3] quit
# Display information about packets forwarded by UDP helper on VLAN-interface 3.
[SwitchA] display udp-helper server interface Vlan-interface 3
Interface name Server VPN Server address Packets
Vlan3 192.168.2.2 5
#
vlan 2 to 3
#
udp-helper enable
udp-helper port 53
#
interface Vlan-interface2
ip address 192.168.2.1 255.255.255.0
#
interface Vlan-interface3
ip address 192.168.1.1 255.255.255.0
udp-helper server 192.168.2.2
#
interface GigabitEthernet3/0/1
port link-mode bridge
port access vlan 3
#
interface GigabitEthernet3/0/2
port link-mode bridge
port access vlan 2
#
· H3C S12500 Routing Switch Series Layer 3—IP Services Configuration Guide
· H3C S12500 Routing Switch Series Layer 3—IP Services Command Reference
