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.