Udp Relay Commands - NETGEAR GSM7224R - ProSafe Switch Cli Reference Manual

This section describes the UDP relay feature in the following subsections:
• Section 17.1 "UDP Relay Configuration Commands" on page 17-2
• Section 17.2 "UDP Relay Show Commands" on page 17-3
The UDP relay (also referred to as IP helper) feature provides a mechanism that allows the
switch to forward certain configured UDP broadcast packets to a particular IP address.
This allows various applications to work across subnets, even if the applications were not
originally designed to do so.
You can configure which UDP ports are forwarded. If you choosenot to specify the UDP
ports, the following UDP ports are forwarded:
• IEN-116 Name Service (port 42)
• DNS (port 53)
• NetBIOS Name Server (port 137)
• NetBIOS Datagram Server (port 138)
• TACACS Server (port 49)
• Time Service (port 37)
The system supports a maximum of 128 interface address-port pairs. For example, you can
have a single UDP port forwarded on 128 different routing interfaces, or you can have 128
UDP ports forwarded on a single routing interface.
When the switch receives a broadcast UDP packet on a routing interface, the UDP port to
IP address mapping table is checked. If that routing interface has an entry, the destination
UDP port is checked against the UDP port list in the table entry. If there is a match, the
packet is forwarded to the configured IP address. Otherwise the packet is not forwarded.
Note that if the configured destination IP address is 0.0.0.0, the packet is not forwarded.
If the receiving routing interface does not have an entry in the UDP port-to-address
mapping table, any entries for 'All' interfaces are checked. For each entry that is
configured for 'All' interfaces, the UDP port list is compared to the destination UDP port
in the packet. If there is a match, the packet is forwarded to the configured IP address.
Otherwise the packet is not forwarded. Note that if the configured destination IP address is
0.0.0.0, then the packet is not forwarded.

UDP Relay Commands

UDP Relay Commands
v1.0, November 2007
Chapter 17
17-1