Alcatel Omni Switch/Router, User Manual

Page: 768 / 1100

BOOTP/DHCP Relay
Page 26-4
BOOTP/DHCP Relay
The switch supports a
UDP
relay function that allows Bootstrap Protocol (
BOOTP
) and
Dynamic Host Configuration Protocol (
DHCP
) packets to pass between AutoTracker Groups.
♦
Note
♦
A
BOOTP
/
DHCP
relay may be configured for authenti-
cated groups as well. See BOOTP/DHCP Relay and
Authentication on page 26-5 and the Authentication
Services chapter of the Switched Network Solutions User
Manual .
Through UI software, you can turn the relay function on or off and specify the IP addresses of
DHCP
servers, the delay before the relay forwards a request, and the maximum number of
hops a packet may be forwarded through the network.
Alternately the relay function may be provided by an external router connected to the switch;
in this case, the relay would be configured on the external router.
Overview of DHCP
DHCP
provides a framework for passing configuration information to Internet hosts on a
TCP/
IP
network. It is based on the Bootstrap Protocol (
BOOTP
), adding the ability to automatically
allocate reusable network addresses and additional configuration options.
DHCP
consists of
the following two components:
• A protocol for delivering host-specific configuration parameters from a
DHCP
server to a
host.
• A mechanism for allocating network addresses to hosts.
DHCP
is built on a client-server model in which a designated
DHCP
server allocates network
addresses and delivers configuration parameters to dynamically configured hosts. It supports
the following three mechanisms for IP address allocation:
Automatic
DHCP
assigns a permanent IP address to a host.
Dynamic
DHCP
assigns an IP address to a host for a limited period of time (or until the
host explicitly relinquishes the address).
Manual
The network administrator assigns a host’s IP address and
DHCP
simply
conveys the assigned address to the host.
A particular network will use one or more of these mechanisms, depending on the policies of
the network administrator.
For information about configuring
DHCP
servers, see the IP Control chapter of the Switched
Network Solutions User Manual .
DHCP and the OmniS/R
The unique characteristics of the
DHCP
protocol require a good plan before setting up the
switch in a
DHCP
environment. Since
DHCP
clients initially have no IP address, placement of
these clients in an AutoTracker
VLAN
is hard to determine. In simple networks (i.e., one
group, one
VLAN
) AutoTracker rules do not need to be deployed to support the
BOOTP/DHCP
relay functionality.