H3C Technologies H3C S5560 Series Switches - Manual (Page 148)

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Configuring UDP helper
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
Layer 3 aggregate interfaces. 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: