Introduction To Udp Helper - H3C S3610-28P Operation Manual

Operation Manual – UDP Helper
H3C S3610&S5510 Series Ethernet Switches
Chapter 1 UDP Helper Configuration
When configuring UDP Helper, go to these sections for information you are interested
in:

Introduction to UDP Helper

Configuring UDP Helper
Displaying and Maintaining UDP Helper
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.
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.
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 List of default UDP ports
Trivial File Transfer Protocol (TFTP)
Domain Name System (DNS)
Time service
NetBIOS name service (NetBIOS-NS)
NetBIOS datagram service (NetBIOS-DS)
Terminal access controller access control system (TACACS)
Table 1-1.
Protocol
1-1
Chapter 1 UDP Helper Configuration
UDP port number
69
53
37
137
138
49