3Com Switch 8800 Advanced Software V5 Configuration Guide

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UDP HELPER CONFIGURATION
When configuring UDP Helper, go to these sections for information you are
interested in:
■ “Introduction to UDP Helper” on page 713
■ “Configuring UDP Helper” on page 713
■ “Displaying and Maintaining UDP Helper” on page 714
■ “UDP Helper Configuration Examples” on page 715
n
UDP Helper can be currently configured on VLAN interfaces only.
Introduction to UDP
Helper
UDP Helper makes the device function as a relay that converts broadcast packets
with the specified UDP destination port number into unicast packets and forwards
them to a specified server.
With UDP Helper enabled, the device decides whether to forward a received UDP
broadcast packet according to its UDP destination port number. If the packet
needs to be forwarded, the device modifies the destination IP address in the IP
header and then sends the packet to the specified destination server. Otherwise,
the device sends the packet to its 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 31.
Configuring UDP
Helper
Follow these steps to configure UDP Helper:
Tab le 31 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
To do... Use the command... Remarks
Enter system view system-view -