3Com 4007, Implementation Manual, Page: 393 / 684

User Datagram Protocol (UDP) Helper
393
User Datagram
Protocol (UDP)
Helper
User Datagram Protocol (UDP) Helper allows TCP/IP applications to
forward broadcast packets from your module (as a router) and to another
part of the network.
Two common uses of the UDP Helper feature are:
■
Bootstrap Protocol (BOOTP)
Using BOOTP through a logical port, you can boot a host through the
router, even if the host is on another part of the network. UDP packets
that rely on the BOOTP relay agent are modified and then forwarded
through the router.
■
Dynamic Host Configuration Protocol (DHCP)
Using DHCP, a host can retrieve its own configuration information,
including the IP address, from a DHCP server through the IP network.
DHCP makes it easier to administer the IP network. With DHCP, you
can dynamically configure a host with new information.
3Com implements a generic UDP Helper agent in the module that can
apply to any UDP port.
Implementing UDP
Helper
You have to set the following UDP Helper parameters:
■
UDP port number — A logical address, not a port (interface) on your
module. BOOTP (including DHCP) uses UDP port 67.
■
IP forwarding address — The IP address to which the packets are
forwarded. You can have up to 63 combinations of port numbers and
IP forwarding addresses per router. You can also have multiple IP
address entries for the same ports.
■
Hop count — The number of interfaces that the module uses to
forward a packet through the router.
■
Threshold — The maximum number of times that the module
forwards a packet to the network. By default, there is no BOOTP relay
threshold. (The default value is
0
.
)
The commands to implement these parameters are described in the “IP
Routing” chapter of the
Command Reference Guide
.
You need to have a thorough understanding of your network
configuration to use UDP Helper. Review the network topology before
you implement UDP Helper.