User Datagram Protocol (Udp) Helper - 3Com corebuilder 3500 Implementation Manual

User Datagram
Protocol (UDP)
Helper
User Datagram Protocol (UDP) Helper allows IP applications to route
broadcast packets from one subnet to another part of the network.
Two common uses of the UDP Helper feature are:
Bootstrap Protocol (BOOTP)
BOOTP allows diskless workstations to obtain their own IP addresses,
the address of a server host, and the name of the boot file, which is
loaded into memory from the server and executed. RFC 951 is the
official specification for BOOTP with clarifications and extensions
provided in RFC 1542.
Dynamic Host Configuration Protocol (DHCP)
DHCP provides a framework for passing configuration information to
hosts on an IP network. DHCP is based on BOOTP, but adds the
capability of automatic allocation of reusable network addresses and
other configuration options. DHCP captures the behavior of BOOTP
relay agents and DHCP participants can interoperate with BOOTP
participants. RFC 2131 is the official specification for DHCP.
Both BOOTP and DHCP use the logical port number 67 for their servers.
However, 3Com implements a generic UDP Helper agent in the system
that can apply to any port.
Implementing UDP Helper
Configure UDP Helper by specifying a logical port number on which to
listen for broadcast IP packets and an IP forwarding address for the
packet.
The system handles the packet based on the way VLANs are set up:
If the broadcast packet is received on the same VLAN as the
forwarding address — Your system bridges the packet.
If the broadcast packet is received on an IP interface that is
associated with a different VLAN than the forwarding address
— Your system updates the BOOTP/DHCP gateway IP address of the
packet to use the interface on which the packet was received; the
system then routes the frame to the forwarding IP address.

User Datagram Protocol (UDP) Helper

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